KR20170019392A - A method for providing downlink control information in a mimo wireless communication system and an appratus for the same - Google Patents

Abstract

The present invention relates to a wireless communication system, and more specifically, to a method and an apparatus for providing downlink control information in an MIMO wireless communication system. According to one embodiment of the present invention, a method for allowing user equipment to receive a downlink signal from a base station in a wireless communication system that supports downlink MIMO transmission includes the steps of: receiving downlink control information including information indicative of the number (N, 1 <= N <= 8) of layers where one or two enabled code words of the downlink MIMO transmission are mapped; receiving downlink data transmitted over the respective N layers and a UE-specific reference signal for each of the N layers, based on the downlink control information; and decoding the downlink data based on the UE-specific reference signal, wherein the information indicative of the number of layers further includes information on a code for identifying the UE-specific reference signals.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for providing downlink control information in a MIMO wireless communication system,

The following description relates to a wireless communication system, and more particularly, to a method and apparatus for providing downlink control information in a MIMO wireless communication system.

In a mobile communication system, a terminal can receive information through a downlink from a base station, and the terminal can also transmit information to a base station through an uplink. The information transmitted or received by the terminal includes data and various control information, and various physical channels exist depending on the type and use of information transmitted or received by the terminal.

The downlink channel may include a downlink control channel and a downlink data channel. The downlink control channel may include a control signal defining a resource allocation and a transmission format for a signal transmitted through a downlink data channel. The control information transmitted through the downlink control channel may be referred to as downlink control information (DCI). The DL control channel may include various DCI formats, and the DCI format may include downlink resource allocation information or uplink resource allocation information.

Meanwhile, a Multiple Input Multiple Output (MIMO) scheme may be applied in uplink or downlink. The MIMO technique refers to a technique of increasing the capacity of a system by simultaneously transmitting a plurality of data streams spatially using two or more transmit / receive antennas at a transmitter and / or a receiver. As a MIMO scheme using multiple transmit antennas, transmit diversity, spatial multiplexing, or beamforming may be used.

In case MIMO scheme is applied to downlink transmission, DCI for downlink MIMO transmission needs to be provided in order for a downlink receiving entity (for example, a UE) to correctly receive downlink transmission.

In the existing 3GPP LTE system, up to two codewords are supported for downlink transmission, and transmission through a maximum of four layers (i.e., transmission of the maximum rank 4) is supported. In the beamforming scheme, Only the forming transmission can be supported. It is discussed that introducing a system capable of providing improved performance over existing 3GPP LTE systems, including dual layer beamforming, maximum rank 8 transmission, UE-specific RS, Based multi-user MIMO.

In the case of downlink transmission using a new MIMO scheme different from the conventional MIMO scheme, the downlink receiving entity may not correctly receive the downlink signal according to the control information according to the DCI format defined in the prior art. Therefore, it is required to design a DCI format capable of providing control information necessary for correct transmission and reception of downlink signals in a downlink MIMO transmission of a new scheme. Accordingly, the present invention provides a method and apparatus for providing downlink control information required for a new downlink MIMO transmission.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, unless further departing from the spirit and scope of the invention as defined by the appended claims. It will be possible.

According to an aspect of the present invention, there is provided a method for receiving a downlink signal from a base station in a wireless communication system supporting downlink multiple input / output (MIMO) Receiving downlink control information including information indicating a number of layers (N, 1? N? 8) to which one or two activated codewords are mapped; Receiving downlink data transmitted on each of the N layers and a UE-specific reference signal for each of the N layers based on the downlink control information; And demodulating the downlink data based on the terminal-specific reference signal, wherein the information indicating the number of layers includes information on a code for identifying the terminal-specific reference signal As shown in FIG.

According to another aspect of the present invention, there is provided a method for transmitting a downlink signal to a mobile station in a wireless communication system supporting downlink multiple input / output (MIMO) Transmitting downlink control information including information indicating the number of layers (N, 1? N? 8) to which one or two enabled codewords are mapped; And transmitting downlink data transmitted on each of the N layers and a UE-specific reference signal for each of the N layers based on the downlink control information, The link data is demodulated by the terminal based on the terminal-specific reference signal, and the information indicating the number of layers may further include information on a code identifying the terminal-specific reference signal .

According to another aspect of the present invention, there is provided a mobile communication system supporting downlink multiple input / output (MIMO) transmission, the terminal receiving a downlink signal from a base station, And a receiving module for receiving downlink data; A transmission module for transmitting uplink control information and uplink data to the base station; And a processor for controlling the terminal including the receiving module and the transmitting module, wherein the processor is operable to determine whether one or two activated codewords of the downlink MIMO transmission (N, 1 &amp;le; N &amp;le; 8) through the receiving module, and transmits, through the receiving module, N Specific reference signal for each of the N layers and the downlink data transmitted on each of the N number of layers, and transmits the downlink data and the downlink data on the basis of the terminal- And the information indicating the number of layers may be configured to demodulate information on a code for identifying the terminal-specific reference signal There can be further included.

According to another aspect of the present invention, there is provided a base station for transmitting a downlink signal to a mobile station in a wireless communication system supporting downlink multiple input / output (MIMO) And a receiving module for receiving uplink data; A transmission module for transmitting downlink control information and downlink data to the terminal; And a processor for controlling the base station comprising the receiving module and the transmitting module, wherein the processor is further configured to determine whether the one or two enabled codewords of the downlink MIMO transmission And transmits the downlink control information including information indicating the number (N, 1? N? 8) through the transmission module, and transmits on the N layers based on the downlink control information And transmit the downlink data and a UE-specific reference signal for each of the N layers through the transmission module. The downlink data may be transmitted to the terminal And the information indicating the number of layers may further include information on a code for identifying the terminal-specific reference signal have.

In the above embodiments of the present invention, the information on the code for identifying the UE-specific reference signal may include one codeword mapped to one layer and two codewords mapped to two layers May be included in information indicating the number of layers.

In the embodiments of the present invention, the information on the code for identifying the UE-specific reference signal may be information for distinguishing the UE-specific reference signals transmitted from the same resource element location.

In the embodiments of the present invention, four different UE-specific reference signals transmitted at the same resource element position may be included in one reference signal group, and the one reference signal group may include the UE- A subgroup is divided into two subgroups according to information on a code for identifying a signal, and one subgroup may include two UE-specific reference signals separated by an orthogonal code.

In the embodiments of the present invention, the downlink control information may further include information indicating an antenna port of the downlink MIMO transmission.

In the embodiments of the present invention, the information indicating the number of layers may be composed of 3 bits.

The foregoing general description and the following detailed description of the invention are illustrative and are for further explanation of the claimed invention.

According to the present invention, there is provided a method and apparatus for providing control information for downlink transmission in a wireless communication system to which a maximum rank 8 transmission, a dual layer beamforming, a UE-specific reference signal based multi-user MIMO, .

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention, illustrate various embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 is a diagram illustrating a structure of a radio frame used in a 3GPP LTE system.
2 is a diagram illustrating a resource grid in a downlink slot.
3 is a diagram showing a structure of a downlink sub-frame.
4 is a diagram illustrating the structure of an uplink subframe.
5 is a block diagram illustrating a MIMO transmission structure.
6 is a diagram illustrating a mapping relationship between a layer and a physical antenna in a MIMO transmission structure.
7 is a diagram for explaining a reference signal pattern in a 3GPP LTE system.
8 and 9 are diagrams for explaining a demodulation reference signal (DMRS) pattern.
10 is a diagram for explaining a method of transmitting and receiving a downlink signal according to an embodiment of the present invention.
11 is a diagram illustrating a configuration of a base station apparatus and a terminal apparatus according to a preferred embodiment of the present invention.

The following embodiments are a combination of elements and features of the present invention in a predetermined form. Each component or characteristic may be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. In addition, some of the elements and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments.

Embodiments of the present invention will be described herein with reference to the relationship between data transmission and reception between a base station and a terminal. Here, the BS has a meaning as a terminal node of a network that directly communicates with the MS. The specific operation described herein as performed by the base station may be performed by an upper node of the base station, as the case may be.

That is, it is apparent that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station can be performed by a network node other than the base station or the base station. A 'base station (BS)' may be replaced by a term such as a fixed station, a Node B, an eNode B (eNB), an access point (AP) Further, the term base station in this document can be used as a concept including a cell or a sector. Meanwhile, the repeater can be replaced by terms such as Relay Node (RN) and Relay Station (RS). The term 'terminal' may be replaced with terms such as User Equipment (UE), Mobile Station (MS), Mobile Subscriber Station (MSS), and Subscriber Station (SS).

In the present invention, the downlink transmission entity may be a base station or a repeater (when a repeater is an entity that transmits an access downlink to a terminal), and a downlink receiving entity may be a terminal or a repeater (a repeater is a backhaul (In the case of the subject receiving the downlink). In the following description, a base station will be described as an example of a downlink transmission entity and a terminal will be described as an example of a downlink receiving entity. However, the present invention is not limited to this, and an arbitrary downlink transmission subject and a receiving subject Can be applied.

The specific terminology used in the following description is provided to aid understanding of the present invention, and the use of such specific terminology may be changed into other forms without departing from the technical idea of the present invention.

In some instances, well-known structures and devices may be omitted or may be shown in block diagram form, centering on the core functionality of each structure and device, to avoid obscuring the concepts of the present invention. In the following description, the same components are denoted by the same reference numerals throughout the specification.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the IEEE 802 systems, 3GPP systems, 3GPP LTE and LTE-Advanced (LTE-Advanced) systems, and 3GPP2 systems, which are wireless access systems. That is, the steps or portions of the embodiments of the present invention that are not described in order to clearly illustrate the technical idea of the present invention can be supported by the documents. In addition, all terms disclosed in this document may be described by the standard document.

The following description will be made on the assumption that the present invention is applicable to a CDMA system such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), and Single Carrier Frequency Division Multiple Access And can be used in various wireless access systems. CDMA may be implemented in radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. The TDMA may be implemented in a wireless technology such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in wireless technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) is a part of E-UMTS (Evolved UMTS) using E-UTRA, adopting OFDMA in downlink and SC-FDMA in uplink. LTE-A (Advanced) is the evolution of 3GPP LTE. WiMAX can be described by the IEEE 802.16e standard (WirelessMAN-OFDMA Reference System) and the advanced IEEE 802.16m standard (WirelessMAN-OFDMA Advanced system). For clarity, the 3GPP LTE standard is mainly described below, but the technical idea of the present invention is not limited thereto.

1 is a diagram illustrating a structure of a radio frame used in a 3GPP LTE system. One radio frame includes ten subframes, and one subframe includes two slots in the time domain. The transmission time of one subframe is defined as a transmission time interval (TTI). For example, one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms. One slot may comprise a plurality of OFDM symbols in the time domain. Since the 3GPP LTE system uses the OFDMA scheme in the downlink, the OFDM symbol represents one symbol period. One symbol may be referred to as an SC-FDMA symbol or a symbol length in the uplink. A resource block (RB) is a resource allocation unit, and includes a plurality of consecutive subcarriers in one slot. The structure of such a radio frame is merely exemplary. Therefore, the number of subframes included in one radio frame, the number of slots included in one subframe, or the number of OFDM symbols included in one slot may be changed in various manners.

2 is a diagram illustrating a resource grid in a downlink slot. One downlink slot includes seven OFDM symbols in the time domain, and one resource block (RB) includes 12 subcarriers in the frequency domain, but the present invention is not limited thereto. For example, one slot includes 7 OFDM symbols in the case of a normal CP (Cyclic Prefix), but one slot may include 6 OFDM symbols in an extended CP (CP). Each element on the resource grid is called a resource element (RE). One resource block includes 12 x 7 resource elements. The number of N ^DLs of resource blocks included in the downlink slot depends on the downlink transmission bandwidth. The structure of the uplink slot may be the same as the structure of the downlink slot.

3 is a diagram showing a structure of a downlink sub-frame. In a subframe, a maximum of three OFDM symbols in the first part of the first slot corresponds to a control area to which a control channel is allocated. The remaining OFDM symbols correspond to a data area to which a Physical Downlink Shared Chanel (PDSCH) is allocated. The downlink control channels used in the 3GPP LTE system include, for example, a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical HARQ indicator channel (Physical Hybrid Automatic Repeat Request Indicator Channel (PHICH)). The PCFICH includes information on the number of OFDM symbols transmitted in the first OFDM symbol of the subframe and used for control channel transmission in the subframe. The PHICH includes an HARQ ACK / NACK signal as a response to the uplink transmission. The control information transmitted through the PDCCH is referred to as downlink control information (DCI).

The DCI includes uplink or downlink scheduling information or includes an uplink transmission power control command for an arbitrary terminal group. The PDCCH includes a resource allocation and transmission format of a downlink shared channel (DL-SCH), resource allocation information of an uplink shared channel (UL-SCH), paging information of a paging channel (PCH), system information on a DL- A set of transmission power control commands for individual terminals in an arbitrary terminal group, transmission power control information, activation of VoIP (Voice over IP), resource allocation of upper layer control messages such as random access response And the like. The PDCCH is transmitted in a combination of one or more contiguous Control Channel Elements (CCEs). The CCE is a logical allocation unit used to provide the PDCCH with a coding rate based on the state of the wireless channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of available bits are determined according to the correlation between the number of CCEs and the coding rate provided by the CCE. The base station determines the PDCCH format according to the DCI transmitted to the UE and adds a cyclic redundancy check (CRC) to the control information. The CRC is masked with an identifier called a Radio Network Temporary Identifier (RNTI) according to the owner or use of the PDCCH. If the PDCCH is for a particular UE, the cell-RNTI (C-RNTI) identifier of the UE may be masked in the CRC. Alternatively, if the PDCCH is for a paging message, a Paging Indicator Identifier (P-RNTI) may be masked in the CRC. If the PDCCH is for system information (more specifically, the System Information Block (SIB)), the system information identifier and the system information RNTI (SI-RNTI) may be masked to the CRC. A random access-RNTI (RA-RNTI) may be masked to the CRC to indicate a random access response that is a response to the transmission of the UE's random access preamble. Also, if the PDCCH is for a transmit power control (TPC) command for the uplink transmit power of the UE, the transmit power control identifier (TPC-RNTI) may be masked in the CRC.

A plurality of PDCCHs can be transmitted in the control domain, and the UE can monitor a plurality of PDCCHs. Here, monitoring refers to the UE attempting to decode each of the PDCCHs according to the DCI format. In the control region allocated in the subframe, the BS does not provide information on where the corresponding PDCCH is located to the UE. The UE monitors a set of PDCCH candidates in a subframe to find its PDCCH. This is called blind decoding. For example, if a CRC error is not detected by demodulating its C-RNTI in the corresponding PDCCH, the UE detects the PDCCH with its DCI. The UE may be configured to receive PDSCH data transmissions signaled on the PDCCH according to various transmission modes, and such settings may be semi-statically specified through higher layer signaling.

4 is a diagram illustrating the structure of an uplink subframe. The UL subframe may be divided into a control region and a data region in the frequency domain. A physical uplink control channel (PUCCH) including uplink control information is allocated to the control region. A physical uplink shared channel (PUSCH) including user data is allocated to the data area. To maintain a single carrier characteristic, one terminal does not transmit PUCCH and PUSCH at the same time. A PUCCH for one terminal is allocated to a resource block pair (RB pair) in a subframe. Resource blocks belonging to a resource block pair occupy different subcarriers for two slots. It is assumed that the resource block pair allocated to the PUCCH is frequency-hopped at the slot boundary.

A MIMO system is a system that applies a technique of collecting a piece of fragmentary data received from various antennas without relying on a single antenna path to receive a message. MIMO technology can be widely used for mobile communication terminals and repeaters because it can improve the data transmission speed in a specific range or increase the system range for a specific data transmission speed. MIMO may also be referred to as a multi-antenna technique.

The MIMO channel matrix according to the number of reception antennas and the number of transmission antennas can be decomposed into a plurality of independent channels. Each independent channel is called a layer or a stream. The rank can mean the number of layers or streams. In the following description, 'Rank' in MIMO transmission indicates the number of paths capable of independently transmitting signals, 'Number of layers' indicates the number of signal streams transmitted through each path, . In general, since the transmitting end transmits a number of layers corresponding to the number of ranks used for signal transmission, the rank has the same meaning as the number of layers unless otherwise specified.

As a MIMO scheme using multiple transmit antennas, transmit diversity, spatial multiplexing, or beamforming may be used.

The transmit diversity scheme has the advantage of realizing highly reliable data transmission without channel related feedback information from the receiver by transmitting the same data information through several transmit antennas.

Beamforming is used to increase the reception SINR (Signal to Interference plus Noise Ratio) of a receiver by multiplying a plurality of transmit antennas by appropriate weights. Generally, in an FDD (Frequency Division Duplexing) system, Since independent channel information is required to obtain a proper beamforming gain, it is possible to receive additional feedback from a receiver to apply beamforming.

Meanwhile, the spatial multiplexing scheme can be distinguished by a spatial multiplexing scheme for a single user and multiple users. Spatial multiplexing for a single user is called SM (Spatial Multiplexing) or SU-MIMO (Single User MIMO), and a method for allocating a plurality of antenna resources of a base station to one user (terminal) It increases in proportion to the number. Meanwhile, spatial multiplexing for multiple users is called Spatial Divisional Multiple Access (SDMA) or Multi-User MIMO (MU-MIMO), and a method of distributing a plurality of antenna resources or wireless spatial resources of a base station to a plurality of users to be.

In the case of using the MIMO scheme, a single code word (SCW) scheme in which N data streams transmitted at the same time are transmitted using one channel encoding block, and N data streams M (MCW) scheme in which a plurality of channel encoding blocks are used. At this time, each channel encoding block generates an independent codeword (Codeword), and each codeword can be designed to be capable of independent error detection.

Conventional MIMO systems are designed based on multiple codeword (MCW) structures. In the multi-codeword structure, a maximum of two codewords can be transmitted at the same time. The MIMO transmission includes Modulation and Coding Scheme (MCS) information on the modulation and coding scheme used by the transmitter, a New Data Indicator (NDI) indicating whether the transmitted data is new data or retransmitted data, And a redundancy version (RV) information about which subpacket is to be retransmitted.

5 is a diagram illustrating a MIMO transmission structure. In a system supporting the MIMO scheme, the transmitter may transmit one or more code words. The codeword is mapped to a transport block from an upper layer and will be described later. FIG. 5 exemplarily shows a system supporting a maximum of two codewords. The one or more codewords may be processed as complex symbols through a scrambling module and a modulation mapper, respectively, after which the complex symbols are mapped to a plurality of layers by a layer mapper, May be multiplied by a selected predetermined precoding matrix according to the state and allocated to each transmit antenna. The processed transmission signals for each antenna are respectively mapped to time-frequency resource elements to be used for transmission by the resource element mapper, and then transmitted through the respective antennas via the OFDM signal generator.

The transfer block to code word mapping relationship will be described. In FIG. 5, two transport blocks (TBs) are mapped to two codewords by a transport block to codeword mapping rule. If two transport blocks are enabled, the mapping of the transport block and codeword may be reversed according to the TB to CW swap flag. The TB-to-C mapping rule can be configured as shown in Table 1 and Table 2 below.

Table 1 shows the case where all of the two transport blocks are enabled. Table 2 shows an example of the transport block to codeword mapping rule for the case where one of the two transport blocks is activated and the other is disabled. .

In Table 2, inactivation of the transport block includes the case where the size of the transport block is zero. When the size of the transport block is 0, the transport block is not mapped to the codeword.

If a signal is transmitted using a single antenna, one codeword is mapped to one layer and transmitted. However, when a signal is transmitted using multiple antennas, the codeword-to-layer mapping rule may be as shown in Tables 3 and 4 according to a transmission scheme.

Table 3 shows an example of transmission of a signal by a spatial multiplexing scheme. Table 4 shows an example of transmission of a signal by a transmit diversity scheme. In Table 3 and Table 4, x ^(a) (i) denotes an i-th symbol of a layer having an index a, and d ^(a) (i) denotes an i-th symbol of a codeword having an index a . The mapping relationship between the number of codewords and the number of layers used for transmission can be known through the 'Number of layers' item and the 'Number of codewords' item of Table 3 and Table 4, and 'codeword-to-layer mapping' It shows how the symbols of each codeword are mapped to layers.

As can be seen from Tables 3 and 4, one codeword may be mapped to one layer on a symbol-by-symbol basis and transmitted. However, as in the second case of Table 4, one codeword may be mapped to a maximum of four layers Or may be distributed and mapped.

The mapping relationship between the layer and the physical antenna will be described with reference to FIG. The following description is exemplary and the mapping relationship between the layer and the physical antenna may take any form. In the following description, it is assumed that a system supporting the MIMO transmission scheme has, for example, four physical transmission antennas. When the rank is 1, one codeword (CW1) is mapped to one layer, and data created in one layer by the precoding technique can be encoded to be transmitted through four transmission antennas. And two codewords CW1 and CW2 are mapped to two layers when the rank is 2 and are mapped to four transmission antennas by a precoder. In case of rank 3, one codeword (CW1) of two codewords is mapped to one layer and the other codeword (CW2) is mapped to two layers by a S / P converter (S / P) A total of two codewords are mapped to three layers and then mapped to four transmission antennas by a precoder. When the rank is 4, an example in which two codewords CW1 and CW2 are respectively mapped to two layers by a S / P converter and a total of four layers are mapped to four transmission antennas by a precoder .

A base station having four transmit antennas can have a maximum of four layers and can have four independent codewords. In FIG. 6, a system configured to have a maximum of only two codewords can be used, for example, . In addition, as described above, the information transmitted through the two codewords CW1 and CW2 can be changed and transmitted.

On the other hand, a precoder is expressed by a matrix of Mt (number of transmit antennas) * v (spatial multiplexing rate) matrix. The precoder uses a set of matrices predetermined by the transmitter / receiver, Adaptively. The set of precoding matrices is called a codebook.

In a conventional 3GPP LTE system, four or more logical antenna ports (e.g., antenna ports 0 to 5) may be used. Here, the division of the antenna port is not a physical division, and therefore, the mapping of each logical antenna index to an actual physical antenna index corresponds to an implementation problem of each manufacturer. The antenna port and the physical antenna do not necessarily have to correspond one to one, and one antenna port may correspond to one physical antenna or an antenna array that is a combination of a plurality of physical antennas.

In the 3GPP LTE system, downlink reference signals include cell-specific reference signals (not related to MBSFN transmission), MBSFN reference signals and UE-specific reference signals associated with MBSFN transmission, Three types of reference signals are used.

The cell specific reference signal is a reference signal using a sequence generated by using the cell ID of each cell as an initial value, and antenna port 0 to 3 may be used for cell specific reference signal transmission. The MBSFN reference signal is used for acquiring downlink channel information for MBSFN transmission and is a reference signal transmitted through antenna port 4. [

The UE-specific reference signal is supported for single antenna port transmission of the PDSCH and may be transmitted via antenna port 5. A UE (User Equipment) can be informed of whether this UE-specific reference signal exists from an upper layer (higher than the MAC layer) and can be used for PDSCH demodulation. The UE-specific reference signal enables beamforming of data transmission for a particular terminal. For example, a base station can create directional transmissions for a particular terminal using an array of adjacently located physical antennas (one antenna port). The signals from the different physical antennas may be set at appropriate phases so that they are all combined at the location of the terminal. This directional transmission is recognized by the terminal as one antenna. Since the beam formed by beamforming experiences different channel responses between the base station and the terminal, the use of a UE-specific reference signal is required in order for the terminal to properly demodulate the beamformed data.

The UE-specific reference signal corresponds to a dedicated reference signal (DRS) or precoded DMRS (precoded demodulation reference signal). When precoded reference signals are used, the number of reference signals corresponding to the spatial multiplexing rate is transmitted.

The UE-specific reference signal may be used for single layer beamforming (beamforming of rank 1 transmission) applications. As described above, since the UE-specific reference signal is precoded by the same precoder as that applied to the data on the PDSCH, the precoding matrix is transparent to the UE. That is, in the case of transmission using the UE-specific reference signal, since the estimated channel includes the precoding weight, single layer beamforming can be implemented without information on precoding. Therefore, a DCI format composed of control signal information that does not include precoding information can be used for single layer beamforming. For example, for single layer beamforming, DCI format 1 or DCI format 1A defined for single antenna port transmission and transmit diversity in the DCI format described above may be used.

In the existing 3GPP LTE (Release 8) system, since only the antenna port 5 is defined as the antenna port through which the UE-specific reference signal is transmitted, when the rank is 2 or more, the cell specific reference signals (antenna ports 0 to 3) It is necessary to transmit the data by using the data. That is, each UE can perform data demodulation using the channel information acquired through the cell specific reference signal and the precoding weight information obtained through the control channel.

Recently, the introduction of dual layer beamforming (or dual stream beamforming) is being discussed in 3GPP LTE Release-9 (release-9). The dual layer beamforming refers to a MIMO transmission scheme supporting maximum rank 2 transmission based on a UE-specific reference signal (DRS or DMRS) and corresponds to the extension of the single layer beamforming described above. According to the double layer beamforming, up to two activated transport blocks are mapped to two codewords, respectively, and transmitted through two layers, and a dedicated reference signal is transmitted for each layer. According to the dual layer beamforming, even if the base station does not notify the respective UEs of the precoding information, the UE uses the channel information acquired through the UE-specific reference signal transmitted for each layer, It is possible to receive the transmission.

The dedicated reference signal for the dual layer beamforming may be designed such that each layer is orthogonal through a technique such as Time Division Multiplexing (TDM) / Frequency Division Multiplexing (FDM) / Code Division Multiplexing (CDM). In the case of transmitting using only a single layer, the performance of data demodulation can be improved by informing a reference signal corresponding to a single layer transmission layer among the dedicated reference signals supporting two layers. Therefore, a bit field is required for indicating a reference signal used for single layer beamforming in the downlink control information.

In addition, the dual layer beamforming can transmit and receive data through two layers or a single layer. The case where different codewords are transmitted through two layers corresponds to a multi-codeword single user-multiple input / output (MCW SU-MIMO). In the case of transmission using a single layer, it can operate as SU-MIMO or multi-user-multiple input / output (MU-MIMO). When data is transmitted to a single user using a single layer, it corresponds to SU-MIMO. The case where two layers are allocated to different users corresponds to MU-MIMO. In the case of MU-MIMO, each UE must be able to separate each layer using channel information acquired through a UE-specific reference signal. Therefore, the Node B provides information indicating the corresponding layer to each UE The terminal can acquire the channel. As described above, since a maximum of two layers are used in the dual layer beamforming technique, a 1-bit information is required for a base station to indicate one of two layers.

DCI format 2A can be used as a control signal for SU-MIMO double layer beamforming transmission. Meanwhile, DCI format for supporting MU-MIMO based on dual layer beamforming should also be determined. Considering supporting SU-MIMO double layer beamforming and dynamic switching of MU-MIMO, SU- It is desirable to design one DCI format for MIMO and MU-MIMO dual layer beamforming transmission so that SU-MIMO and MU-MIMO can be distinguished within the corresponding DCI format.

Also, the operation of the 3GPP LTE Release-9 system may be defined to be included in the operation of the Release-10 system. That is, the double layer beamforming transmission operation defined in 3GPP LTE Release-9 needs to be defined to operate without problems even in the environment of 3GPP LTE Release-10 system. In this regard, it is necessary to consider that the overhead of the DRS pattern of the 3GPP LTE Release-10 system (i.e., the number of downlink resource elements to which DRS is transmitted) is changed according to the transmission rank. In the 3GPP LTE Release-10 system, for example, the DRS overhead remains the same from rank 1 to rank 2, the DRS overhead of rank 3 and above is increased over the DRS overhead to rank 2, and the rank 3 to rank 8 A DRS pattern can be designed to have the same DRS overhead. Alternatively, the DRSs of rank 1 through rank 4 have the same overhead, the DRS overheads of rank 5 and above are increased over the DRS overhead up to rank 4, and the DRS patterns May be designed. In the 3GPP LTE Release-9 system, the dual layer beamforming is designed to have a maximum rank of 2, and in the MU-MIMO scheme, a single layer is assigned to each UE. At this time, the DRS overhead of the rank 2 can be maintained even in the case of performing the MU-MIMO operation. Meanwhile, since the 3GPP LTE Release-10 system supports maximum rank 8 transmission, layers smaller than 8 can be allocated to each UE when MU-MIMO transmission is applied. Therefore, in the case of the maximum rank 8 transmission, the total transmission rank used for transmission, the transmission rank for each terminal, and the information of the layer allocated to each terminal must be known before the MU-MIMO operates correctly .

The DRS pattern of 3GPP LTE Release-9 can be configured as a subset of the DRS pattern of Release-10, and the transmission mode defined in Release-9 is defined as one of the transmission modes defined in Release-10 . In this case, a DCI format for only dual layer beamforming of Release-9 may be configured. Hereinafter, the design of the DCI format capable of simultaneously supporting SU-MIMO and MU-MIMO in the release-9 transmission mode will be described.

Configuration of bit field in DCI format

Hereinafter, an embodiment of the present invention in which a field defined in an existing DCI format is newly analyzed to support double layer beamforming will be described. 1, 1A, 1B, 1C, 1D, 2, 2A, 3 and 3A in the existing 3GPP LTE standard (for example, 3GPP LTE Release-8). DCI formats 1 and 2 are for downlink resource allocation information, and DCI formats 3 and 3A are uplink TPCs for arbitrary UE groups. transmit power control) command.

Table 5 shows the downlink control information (DCI) format 2A defined in the existing 3GPP LTE standard (Release 8).

The DCI format 2A corresponds to a control information format for two codeword-only loop-space multiplex transmission. Open loop spatial multiplexing transmission means that spatial multiplexing transmission is implemented without feedback from the terminal. In this sense, the open loop scheme may be expressed as using non-channel dependent precoding.

The transmission mode can be semi-statically changed by higher layer signaling, and when the terminal is defined as a dual layer beamforming, when the terminal interprets the DCI format 2A, the open- To interpret the bit fields of DCI format 2A as a different meaning than the control information for DCI format 2A.

DCI format 2A supports up to two codewords (transport blocks), and defines MCS, NDI, and RV for each transport block. As described above, the MCS is information on the modulation and coding scheme used by the transmitting end. The NDI is a new data indicator indicating whether the data to be transmitted is new data or retransmitted data. In case of retransmission, the RV indicates which subpacket is retransmitted Means the redundancy version information.

The 2 ^N fields of the MCS composed of N bits can be expressed by a modulation order and a transport block size. Some fields are used to represent modulation and coding schemes used for data transmission, and some fields only represent modulation orders, which can be used in retransmission. Also, some fields indicate a '0' transport block size, which indicates that no data transmission is occurring. When a field of an MCS having a transport block size of '0' (zero) is indicated, it may mean that the transport block is deactivated. Alternatively, when a field of an MCS having a non-zero transport block size is indicated, it may mean that the transport block is activated.

On the other hand, the transport block to codeword swap flag indicates whether or not to swap the mapping relation between two codewords of two transport blocks as described in Table 1. [

Precoding information defined in DCI format 2A provides information on the transmission rank. The precoding information is set to 0 bit (i.e., not present) for transmission by two antenna ports, and is set to 2 bits for transmission by four antenna ports. The contents of the precoding information field for 4 antenna ports can be defined as shown in Table 6 below.

In case of DCI format 2A, transmission diversity transmission is performed in case of rank 1 (when one code word is activated), and spatial multiplexing transmission is performed in case of rank 2 with two code words. The manner of applying transmit diversity or spatial multiplexing according to the rank can be determined as shown in Tables 7 and 8 below.

Table 7 shows a case where one of the two transport blocks is enabled, and Table 8 shows a case where both of the two transport blocks are activated. In the case of Table 7, a transport block-to-code word swap flag is not needed, but in the case of Table 8, a transport block-to-code word swap flag is required to determine which codeword is mapped to two transport blocks Do.

The indication to the rank can be made explicitly or implicitly. The explicit rank indication may be by a method of defining a separate rank indicator.

On the other hand, the terminal may acquire information on the rank in an implicit manner without setting a rank indicator. In this connection, the MCS information of the transport block and the RV indicate whether or not the transport block is activated. In the DCI format 2A, for example, when the value of the MCS index of the transport block is set to '0' to indicate that the transport block size is 0, it means that the transport is not performed, so that it can be indicated that the transport block is inactivated. If the size of the transport block is not 0, it can indicate that the transport block is activated. Alternatively, it may indicate that the transport block is deactivated when the value of the MCS index is set to 0 and the RV is set to 1, and in the remaining cases, the transport block may be activated. Accordingly, the UE can implicitly know that it corresponds to the rank 2 transmission when all of the two transport blocks are activated, and corresponds to the rank 1 transmission if one of the two transport blocks is activated and the other is inactivated.

According to the definition of the existing DCI 2A format, when only one transport block of two transport blocks is activated, the transport block to code word swap flag is reserved, so that the transport block-to- Can be defined to be interpreted as representing meaning.

For example, in the case of rank 1 transmission, the transport block-to-code word swap flag of DCI format 2A may be used as information indicating an index to a transport block, codeword or layer used for single layer beamforming have.

Alternatively, the transport block-to-codeword swap flag may be used as an indicator to indicate whether the DRS overhead is changed in using DRS defined in 3GPP LTE Release-9 and Release-10. For example, if the DRS overhead of 3GPP LTE Release-10 is increased relative to the DRS overhead of Release-9, then some of the resource elements (REs) not used for DRS in Release- If the Release-9 UE does not recognize this, it is interpreted that other information (for example, data) other than RS is transmitted on the corresponding resource element, so that the UE can not correctly receive the downlink signal It is possible. Therefore, in the case of setting the DRS overhead to be notified to the UE through the transport block-to-code word swap flag, the Release-9 UE determines that the resource element location to which the RS defined in Release- (Null RE), so as to correctly receive the downlink signal.

Alternatively, in case of Rank 1 transmission, the transport block-to-code word swap flag may be used as a flag indicating whether the rank 1 transmission is a single layer beamforming transmission or a transmission diversity transmission.

In the following, in addition to the above-mentioned proposals, various embodiments of the present invention for newly interpreting the bit field of the DCI format 2A will be described in more detail.

Embodiment 1

An embodiment of the present invention for newly analyzing some bit fields of the DCI format 2A will be described.

In the following embodiments, whether or not only one transport block of two transport blocks is activated may be notified to the UE via explicit signaling, or implicitly (i. E., The MCS value and / or the RV value of the transport block It may be notified to the terminal.

Embodiment 1-1 uses a transport block to code word swap flag as a codeword indicator.

According to the definition of the existing DCI 2A format, when only one transport block of two transport blocks is activated, the transport block to codeword swap flag is reserved, and both transport blocks 1 and 2 are mapped to codeword 0 (See Table 2). In this embodiment, when only one of the two transport blocks is activated, a scheme of using a transport block to code word swap flag as an indicator for a code word to which one transport block is mapped is proposed. That is, the transport block to codeword swap flag can be reused as information indicating an index to a codeword used for single layer beamforming.

According to the present embodiment, when only one of the two transport blocks is activated, the transport block to codeword swap flag can be defined to be given as a one bit value without being reserved. Accordingly, when the logical value of the swap flag is the first value when only one of the two transport blocks is activated, the transport block 1 is mapped to the codeword 0 if only the transport block 1 is activated, and when the transport block 1 is activated, It can be interpreted as mapping block 2 to code word 1. If only one of the two transport blocks is activated and the logical value of the swap flag is the second value, if only the transport block 1 is activated, the transport block 1 is mapped to the codeword 1, and if only the transport block 2 is activated, Can be interpreted as mapping to code word 0.

The first logical value of the swap flag may correspond to 0 or off and the second logical value may correspond to 1 or on. The first and second logical values may have any form of 1/0 or on / off, and are not limited to the example described above. That is, the first logical value may correspond to 1 or on and the second logical value may correspond to 0 or off.

The meaning indicated by the logical value of the first value or the second value can be similarly applied to other bit fields in the following embodiments of the present invention. That is, any bit field having a logic value of a first value or a second value means that it has a logic value such as 1/0 or on / off.

Tables 9 and 10 show the transfer block to code word mapping relationship for the embodiment 1-1.

Embodiment 1-2 uses the transport block to codeword swap flag as a codeword indicator.

According to the present embodiment, when only one of the two transport blocks is activated, the transport block to codeword swap flag can be defined to be given as a one bit value without being reserved. If only one of the two transport blocks is activated and the logical value of the swap flag is the first value (0 or off), the activated transport block can be interpreted as being mapped to code word 0. On the other hand, if only one of the two transport blocks is activated and the logical value of the swap flag is the second value (1 or on), it can be interpreted that the activated transport block is mapped to codeword 1. Tables 11 and 12 show the transmission block to codeword mapping relationship for the embodiment 1-2.

Embodiment 1-3 uses a transport block to code word swap flag as a layer indicator.

According to the present embodiment, when only one of the two codewords is activated and the other codeword is deactivated, if the logical value of the swap flag is the first value (0 or off) It can be interpreted that the channel information of the second layer is obtained when the logical value of the swap flag is the second value (1 or on).

On the other hand, when only one of the two codewords is activated, if it is indicated to be transmitted in the transmit diversity scheme, a two-layer based transmit diversity scheme can be applied. The terminal can acquire channel information for two channels from a dedicated reference signal transmitted through each layer. In this case, the codeword-to-layer mapping relationship may follow the mapping relationship shown in Table 4 above.

Embodiment 1-4 is for reusing a new data indicator (NDI) or a redundancy version (RV) field of a transport block to be deactivated.

As described above, in DCI format 2A, MCS, NDI, and RV fields are defined for a transport block. When one transport block of two transport blocks is activated and the other transport block is inactivated, the NDI field or RV field of the transport block to be deactivated may be used for other purposes. Activation of the transport block may be set such that the transport block is deactivated when the MCS index value of the transport block is 0, or when the MCS index value is 0 and the RV value is 1, as described above.

Since a maximum of two layers are used in the dual layer beamforming scheme, the base station can use one field of the DCI information to indicate one layer or antenna port used for single antenna port transmission among the two layers. For example, as shown in Table 13, when the NDI value of the deactivated transport block is the first value (or 0), it indicates that the layer used for transmission is the first layer, 2 (or 1), it can be interpreted as indicating that the layer used for transmission is the second layer.

On the other hand, instead of using the NDI field of the inactive transport block, the layer may be indicated by using the RV field. When the MCS index value of the transport block is 0 and the transport block indicates inactivation, the first layer is indicated when the RV field value of the deactivated transport block is the first value (or 0), and the RV field value (Or 1), it may be interpreted as indicating the second layer.

As Embodiment 1-4-1, the layer number (or index) to which the activated transport block is mapped can be designated through the NDI or RV field of the deactivated transport block. As described in Table 5, the NDI field of the DCI format 2A has a size of 1 bit, and the RV field has a size of 2 bits. Therefore, all or a part of the total of 3 bits for NDI and RV related to the deactivated transport block can be used to indicate a layer used for transmission.

For example, a transmission scheme that supports a maximum of two ranks uses two layers. In this case, one bit of bits for NDI or RV may be used to indicate whether the layer used for transmission is layer 1 or layer 2. For example, a transmission scheme that supports up to four ranks uses four layers. In this case, 2 bits of the bits for the NDI or RV can be used to indicate which layer is used in the first to fourth layers. For example, a transmission scheme that supports up to eight ranks uses eight layers. In this case, 3 bits of bits for NDI or RV may be used to indicate which layer is used in the first to fourth layers.

As Embodiment 1-4-2, the number (or index) of the layer group to which the activated transport block is mapped can be designated through the NDI or RV field of the inactivated transport block. For example, the layers used for transmission may be divided into N groups, and M bits may be used among the total of 3 bits for NDI and RV to indicate which layer group among the N layer groups is used for transmission .

For example, if you divide four layers into two groups, you can use 1 bit to tell the layer group index. For example, if you divide eight layers into four groups, you can use two bits to tell the layer group index. For example, if you divide eight layers into two groups, you can use one bit to tell the layer group index.

As Embodiment 1-4-3, it is possible to notify whether the RS overhead is changed through the NDI or RV field of the deactivated transport block. As described above, the overhead of DRS may vary depending on the overall transmission rank, and DRS according to rank may be defined in 3GPP LTE release-10 but not in release-9. Therefore, when the Release-9 terminal operates in the Release-10 system, the RS may be transmitted beyond the RS overhead that the Release-9 terminal can recognize. In this case, if the RS is transmitted to the resource element (RE) area recognized as data by the release-9 user, a serious problem may occur in receiving data from the position of the release-9 terminal. Therefore, it is necessary to inform the release-9 terminal whether or not there is a resource element (RE) in which data transfer is not performed.

For this purpose, one of the bits for the NDI and / or RV of the deactivated transport block may be used to indicate whether the overhead of the RS has changed. If the flag for the RS overhead change has a first value (e.g., on), then the Release-9 terminal may act to not read the data in the resource element (RE) of the location where the RS is transmitted in the Release-10 system have. Also, when calculating the Effective Coding Rate, the number of subcarriers can be calculated in consideration of the increased RS overhead. The effective coding rate can be calculated according to the burst size / (number of subcarriers x modulation order) (burst size / (number of subcarriers x modulation order).

As Embodiments 1-4-4, the NDI or RV field of the deactivated transport block can be used as an indicator of transmit diversity transmission.

In the case of using two antenna ports as described above, the precoding information field of DCI format 2A is not defined. According to the conventional DCI format 2A, a precoding information field is not defined for a 2-Tx antenna transmission. When one codeword is activated (i.e., in case of rank 1), it is defined to operate according to a transmission diversity scheme have. When this DCI format 2A is used for double layer beamforming, uncertainty occurs in the transmission of rank 1. That is, there is a problem that it is not clearly indicated whether the rank 1 transmission is the transmission diversity transmission or the rank 1 beam forming.

Specifically, when the precoding information field is not defined, it is possible to know whether the two-codewords are both active or not, whether they are rank-1 beamforming or rank-2 beamforming. In this regard, it is necessary to define transmission diversity as a basic transmission scheme even in the dual layer beamforming scheme. Since the transmission diversity scheme also corresponds to rank 1 transmission, only one code word is inactivated, It can not be reliably indicated whether it is a transmission diversity scheme or a transmission diversity scheme. Therefore, it is necessary to reliably indicate whether it is transmit diversity transmission or rank one beamforming when one codeword is inactivated.

For this purpose, it may be defined to indicate whether transmission diversity transmission is performed using the NDI or RV field of the inactive transmission block. For example, if the NDI value of the inactive transport block is a first value, it indicates transmission diversity transmission, and if the NDI value is a second value, it indicates that it is a rank 1 beam forming. In the case of transmit diversity transmission, the UE may be configured to perform data demodulation using a cell specific reference signal (CRS), or may perform data demodulation using a dedicated reference signal (DRS) for two layer transmission .

Embodiment 1-5 is directed to supporting operation in which the RS defined in the 3GPP LTE Release-10 recognizes the position of a resource element to be transmitted as a null resource element (null RE). To this end, the transport block to codeword swap flag can be used as an indicator to indicate whether there is a null resource element (RE) for DRS transmission defined in release-10.

For example, if the transport block versus code word swap flag has a first value (e.g., 0), it may indicate that a Release-9 DRS pattern is used. In this case, when the transport block 1 is activated and the transport block 2 is inactivated, it is transmitted through the layer 0, and when the transport block 1 is inactivated and the transport block 2 is activated, it can be set to be transmitted through the layer 1.

For example, if the transport block to code word swap flag has a second value (e.g., 1), then a release-9 DRS pattern may be used to indicate that a null resource element (null RE) is present. In this case, when the transport block 1 is activated and the transport block 2 is inactivated, it is transmitted through the layer 0, and when the transport block 1 is inactivated and the transport block 2 is activated, it can be set to be transmitted through the layer 1.

In Embodiments 1-5, the transport block and codeword mapping relationship may be set as shown in Table 2 above.

Embodiment 1-6 uses the transport block to codeword swap flag field as an indicator indicating a transmission mode.

In this embodiment, when only one transport block of two transport blocks is activated, one of the transport diversity scheme and the single layer beamforming scheme can be designated according to the value of the transport block to code word swap flag. For example, it may indicate a transmit diversity scheme when the transport block to code word swap flag value is a first value (e.g., 0). And a single layer beamforming scheme when the swap flag value is a second value (for example, 1). In this case, when the transport block 1 is activated and the transport block 2 is inactivated, it is transmitted through the layer 0, and when the transport block 1 is inactivated and the transport block 2 is activated, it can be set to be transmitted through the layer 1.

Embodiment 1-7 is a new interpretation of the precoding information field defined in DCI format 2A for double layer beamforming.

In the DCI format 2A defined for open loop spatial multiplexing, the precoding information field is set to 0 bits for 2 antenna port transmissions and 2 bits for 4 antenna port transmissions. Since the dual layer beamforming transmission mode uses a maximum of 2 antenna ports, the 'precoding information' field can be set to 0 bits because the precoding information field is unnecessary as described above. In the dual layer beamforming transmission mode, It can be defined not to interpret even if a bit for the coding information field is assigned.

In the conventional DCI format 2A, as shown in Table 6, a bit field reserved in the precoding information field for 4 antenna ports (for example, bit fields 2 and 3 when one codeword is activated, When the codeword is activated, bit field 3) is present. These reserved bit fields may be defined for dual layer beamforming.

According to the DCI format 2A as described above, when only one codeword of two codewords is activated as described above, it can be interpreted to mean single layer precoding, or it can be interpreted as a transmission diversity scheme The number is ambiguous. Therefore, it is required to provide the downlink control information so that the ambiguity can be solved when the double layer beamforming is applied. In the following, various schemes of the present invention for defining some of the reserved fields of the precoding information field for four antenna ports for double layer beamforming will be described.

As shown in Table 14 below, when only one codeword is activated, it can explicitly indicate 'single layer precoding' through a predetermined bit value of the precoding information field for 4 antenna ports.

Or, it may indicate whether or not the RS overhead is changed in the precoding information field for four antenna ports as shown in Table 15 below. Specifically, when the Release-9 terminal is operating in the 3GPP LTE Release-10 system, a change may occur in the RS overhead as described above. In this case, since the RS position additionally defined for the Release-10 UE is unknown to the Release-9 UE, severe performance degradation may occur in downlink data demodulation of the Release-9 UE. Therefore, it is necessary to inform the Release-9 UE of information about the increased RS overhead, and to use the predetermined bit values of the precoding information field for the 4-antenna port of the DCI format 2A to perform Rank 1 precoding and Rank 2 Information on increased RS overhead in precoding can be provided.

Alternatively, as shown in Table 16 below, it indicates that the precoding information field for the 4-antenna port is single layer precoding, and that a layer corresponding to single layer precoding is one of the first and second layers (layer 0 or layer 1) May be indicated.

In Table 16, when only one codeword is activated, bit field 0 of the precoding information field indicates transmit diversity. In this case, the UE may be configured to perform data demodulation using a cell specific reference signal (CRS), or may be configured to perform data demodulation using a dedicated reference signal (DRS) for two-layer transmission.

Alternatively, as shown in Table 17 below, it is indicated whether or not the RS overhead is changed in the precoding information field for the 4-antenna port, and at the same time, a layer corresponding to single layer precoding is assigned to the first and second layers (layer 0 or layer 1) Or the like.

In Table 17, only one codeword is activated and, in the case of a transmit diversity transmission, the UE may be configured to perform data demodulation using a cell specific reference signal (CRS) May be set to perform data demodulation using a dedicated reference signal (DRS).

According to an embodiment of the present invention, a DCI format capable of simultaneously supporting SU-MIMO and MU-MIMO in a dual layer beamforming is provided. That is, the DCI format used for the dual layer beamforming and the single layer beamforming may have the same bit field size, and switching between them may be performed using the PDCCH including the modified DCI format 2A proposed in the present invention Can be performed dynamically via transmission.

Embodiment 2

Next, another embodiment of the present invention will be described in which a bit field of the existing DCI format 1A or DCI format 1D is newly analyzed for double layer beamforming.

Table 18 shows DCI formats 1 and 1A defined in the existing 3GPP LTE standard (e.g., 3GPP LTE Release-8). The DCI format 1 / 1A includes control information used in rank 1 transmission such as single antenna, single stream, and transmit diversity transmission.

The DCI format 1A is defined for compact scheduling of one PDSCH codeword in various transmission modes and can be used for transmission diversity transmission. The present invention proposes a new interpretation method for the DCI format 1A for the dual layer beamforming. In the case where the terminal interprets the DCI format 1A as described above, when the dual layer beamforming is defined as the transmission mode (the transmission mode is set semi-statically by the upper layer signaling as described above) Some bit fields can be interpreted.

Among the fields defined in the conventional DCI format 1A, the flag for format 0 / format 1A is set to 1 bit, and the flag for format 0 / format 1A discrimination is set to 1 bit. A value of 0 indicates format 0, and a value of 1 indicates format 1A. Format 1A is used for a random access procedure initiated by a PDCCH order only if Format 1A CRC is scrambled with C-RNTI.

Also, among the fields defined in the existing DCI format 1A, the 'Localized / Distributed VRB assignment flag' is set to 1 bit, and the 'Format 0 / Format VRB assignment flag' Flag &quot; is set to &quot; 1 &quot; (that is, when it indicates format 1A). In other cases (that is, in the case of indicating format 0), a value of 'local type / distributed VRB allocation flag' indicates a local type VRB allocation, and a value 1 indicates a distributed type VRB allocation.

Embodiment 2-1 of the present invention newly analyzes 'flag for format 0 / format 1A distinction' for double layer beamforming. For example, if the logical value of the 'format 0 / flag for format 1A distinction' is a first value, it indicates transmission diversity transmission, and if the logical value is a second value, it indicates a single layer beamforming transmission. As described above, the first value of a logical value of a certain bit field may indicate 0 or off, the second value may indicate 1 or on, and vice versa.

Alternatively, if the logic value of the 'format 0 / flag for format 1A distinction' is the first value, the first layer (layer 0) is indicated in the dedicated reference signal pattern. If the logical value is the second value, 1) can be newly defined.

Alternatively, if the logical value of the 'Format 0 / Flag for format 1A distinction' is a first value, then a Release-9 DRS pattern is used; if the logical value is a second value, -10 may be defined to indicate that nulling is applied to the resource element (RE) to which the DRS added is transmitted.

Example 2-2 is a new interpretation of the 'local / distributed VRB allocation flag' for the dual layer beamforming.

For example, it may indicate that the logical value of the 'local type / distributed VRB allocation flag' is the first value and indicates that it is a single layer beamforming transmission if the logical value is the second value.

(Layer 0) in the dedicated reference signal pattern when the logical value of the 'local type / distributed VRB allocation flag' is the first value, and the second layer (layer 1) when the logical value is the second value. Lt; / RTI &gt;

Alternatively, a release-9 DRS pattern is used when the logical value of the 'local type / distributed VRB allocation flag' is the first value, and a release-9 DRS pattern is used when the logical value is the second value. 10 may be defined to indicate that nulling is applied to the resource element RE to which the DRS added is transmitted.

Embodiment 2-3 is a new interpretation for the dual layer beamforming of two bits for the 'format 0 / flag for discrimination of format 1A' and the 'local / distributed VRB allocation flag'.

For example, one bit out of two bits for the 'format 0 / flag for format 1A distinction' and 'local type / distributed VRB allocation flag' may represent transmit diversity or single layer beamforming. Herein, when a single layer beamforming is indicated, the remaining one bit may represent one of the first layer or the second layer in the DRS pattern.

Alternatively, one bit out of the two bits for 'format 0 / flag for format 1A distinction' and 'local type / distributed VRB allocation flag' may represent transmit diversity or single layer beamforming. Herein, when a single layer beamforming is indicated, the remaining one bit may indicate whether nulling is applied to the resource element RE to which the DRS added in Release-10 is transmitted.

Or, 1 bit out of 2 bits for 'flag for format 0 / format 1A distinction' and 'local type / distributed VRB allocation flag' represents the first layer (layer 0) in the dedicated reference signal pattern, And a second layer (layer 1) if it is a second value. At this time, the remaining one bit may indicate whether nulling is applied to the resource element (RE) to which the DRS added in Release-10 is transmitted.

Table 19 shows the DCI format 1D defined in the existing 3GPP LTE standard (Release 8).

The existing DCI format 1D is defined for compact scheduling of one PDSCH codeword with precoding and power offset information and may be used for multiuser MIMO (MU-MIMO) transmission. In the present invention, new DCI format 1D is proposed for double layer beamforming. In the case where the dual layer beamforming is defined as the transmission mode, the terminal may interpret some bit fields in a different meaning from the MU-MIMO in interpreting the DCI format 1D.

Among the fields defined in the conventional DCI format 1D, the 'TPMI information for precoding' field for precoding indicates the codebook index used for transmission, and the number of antenna ports of the base station is 2 &lt; / RTI &gt; bit for an antenna port, and 4 bits for a 4 antenna port.

According to the embodiment 2-4 of the present invention, the 'TPMI information for precoding' field of DCI format 1D can be newly analyzed for double layer beamforming.

For example, one bit may be used in the 'TPMI information for precoding' to indicate transmit diversity transmission or single layer beamforming. If the logical value of 1 bit in the 'TPMI information for precoding' field given as 2 bits or 4 bits is the first value, it indicates transmission diversity transmission. If the logical value is 1, it indicates that it is a single layer beamforming.

Alternatively, 1 bit is used in the 'TPMI information for precoding', and if the 1-bit logical value is the first value, the first layer (layer 0) in the dedicated reference signal pattern and the second value Layer 1).

Alternatively, 1 bit may be used in 'TPMI information for precoding' to indicate whether nulling is applied to a resource element (RE) to which a DRS added in Release-10 is transmitted.

Alternatively, using 2 bits of 'TPMI information for precoding', 1 bit of them indicates transmission diversity transmission or single layer beamforming, and the remaining 1 bit indicates the first layer or the second layer Lt; / RTI &gt;

Alternatively, two bits of 'TPMI information for precoding' are used, one of which indicates transmission diversity transmission or single layer beamforming, and the remaining one bit indicates a resource element May indicate whether nulling for RE is applied.

Alternatively, two bits of 'TPMI information for precoding' are used, one of which represents the first layer or the second layer in the dedicated reference signal pattern, and the remaining one bit indicates that the DRS added at Release- Or whether nulling of the resource element (RE) to be applied is applied.

Embodiment 3

Hereinafter, another embodiment of the present invention for defining a new DCI format for double layer beamforming will be described.

In the transmission of the dual layer beamforming scheme, two activated transport blocks can be mapped to two code words and transmitted through two layers. Also, the terminal can perform data demodulation using the channel information acquired through the reference signal transmitted for each layer. MCS, NDI and RV are defined for each transport block to transmit two transport blocks. In addition, a transport block to codeword swap flag is defined that can change the relationship that two transport blocks are mapped to two codewords, and more robust data transmission can be achieved through swapping of transport block to codeword mappings.

The dedicated reference signal for the dual layer beamforming may be designed such that each layer is orthogonal through a technique such as Time Division Multiplexing (TDM) / Frequency Division Multiplexing (FDM) / Code Division Multiplexing (CDM). In the case of transmitting using only a single layer, the performance of data demodulation can be improved by informing a reference signal corresponding to a single layer transmission layer among the dedicated reference signals supporting two layers. Therefore, a bit field is required for indicating a reference signal used for single layer beamforming in the downlink control information.

When designing a new (or modified) DCI format for dual layer beamforming based on DCI format 2A, consider the following:

As described above, the dual layer beamforming has a maximum rank of 2, and the rank is equal to the number of the transmission blocks used for transmission, so a separate indicator for the transmission rank is unnecessary. In addition, the UE can know that the corresponding transport block is deactivated according to whether the value of the MCS index of one transport block is set to 0 (or the value of the MCS index is 0 and the RV value is set to 1). Accordingly, the UE can implicitly recognize that it corresponds to rank 1 when one of the two transport blocks is deactivated, and corresponds to rank 2 when both transport blocks are activated. In addition, when a dedicated reference signal (precoded UE-specific reference signal) is used for each layer, it is not necessary to designate a weighting matrix used for precoding. Therefore, in the case of a dual layer beamforming using a dedicated reference signal The precoding information field in the downlink control information (DCI) format need not be defined.

In addition, when a dual layer beamforming transmission mode is used (the transmission mode is set semi-statically by higher layer signaling), a dedicated reference signal is used for the dual layer beamforming, Data can be received by the layer. When a dual layer is used, it operates as SU-MIMO, and when a single layer is used, it can operate as SU-MIMO or MU-MIMO. In order to avoid distinction between SU-MIMO and MU-MIMO in double layer beamforming, it may be considered to use the same DCI format for both. That is, in the dual layer beamforming and single layer beamforming, control information is transmitted by the DCI having the same bit field size, and some of the bit fields used for the dual layer beamforming are used for single layer beamforming Can be interpreted as an indicator.

In addition, when a dual layer beamforming transmission mode is used, a compact DCI format may be defined for a terminal receiving only a single layer.

An example of a new DCI format that satisfies the above considerations with reference to Table 20 will now be described. The DCI format shown in Table 20 includes many of the same fields as the DCI 2A described above, and the following description will focus on the differences between the new DCI format and the conventional DCI 2A format.

The DCI format of Table 20 is for providing control information for single-layer beamforming and dual-layer beamforming. A resource block assignment, a TPC command for PUCCH for a PUCCH, a downlink assignment index, a HARQ process number (for example, An MCS index, a new data indicator (NDI), a redundancy version, and precoding information for each of the transport blocks 1 and 2 can be defined. These fields are defined in the existing DCI format 2A Lt; / RTI &gt; Of these, the precoding information field is set to 0 bits as described above.

Unlike the conventional DCI format 2A, in the DCI format of Table 20, a 'transport block to codeword swap flag' is used for double layer beamforming. In the case of a single layer beamforming transmission, the 'transport block to code word swap flag' may be interpreted as a 'layer indicator.'

When both transport blocks are activated, the 'transport block to code word swap flag' can be used as information indicating the mapping relationship between the transport block and the codeword, and the mapping relation can be defined as shown in Table 1 .

When one transport block is activated and another transport block is deactivated, the activated transport block may be mapped to codeword 0 as shown in Table 2 above. In the case of a single layer beamforming in which only one code word is activated, the 'transport block to code word swap flag' is interpreted as a 'layer indicator'. (Layer X) when the logical value of the layer indicator is the first value (0 or off) and a second layer (layer Y) when the logical value of the layer indicator is the second value (1 or on). Alternatively, in the logical value of the layer indicator, the first value may represent 1 or on, the second value may represent 0 or off, and may represent a corresponding relationship with the first and second layers, respectively. The interpretation of such a layer indicator can be set as shown in Table 21 below.

The layer indicator may also be referred to as an 'antenna port indicator' or 'RS position', and may be referred to as a layer / antenna port corresponding to an activated codeword or a layer Or an antenna port). The terminal can distinguish which layer the channel information valid for itself is obtained through information obtained from the layer indicator.

According to the new DCI format defined as shown in Table 20, the DCI format for the dual layer beamforming and the single layer beamforming can be set to have the same size, and the dynamic mode adaptation of SU-MIMO and MU-MIMO ), Dynamic rank adaptation of rank 1 and rank 2 can be implemented.

Next, another embodiment of a new DCI format satisfying the above-described consideration with reference to Table 22 will be described. Descriptions of portions common to Table 20 in the DCI format shown in Table 22 are omitted for brevity.

In the DCI format shown in Table 22, 'transfer block to code word swap flag' is defined in the same manner as in the conventional DCI format 2A. That is, the transport block to codeword swap flag is used for the dual layer beamforming, and when two codewords are activated, it can be used as information indicating the mapping relationship between the transport block and the codeword, 1 &lt; / RTI &gt; On the other hand, when one transport block is activated and another transport block is inactivated, the activated transport block can be mapped to codeword 0 as shown in Table 2 above.

In the DCI format of Table 22, when the MCS index value of one transport block is set to 0 (or the MCS index value is 0 and the RV value is 1) to indicate that the corresponding transport block is activated and another transport block is deactivated , The UE may implicitly acknowledge that it is a single layer beamforming transmission.

The new data indicator (NDI) field for the deactivated transport block may be interpreted as a layer indicator of the activated transport block. For example, when the transport block 1 is activated and the transport block 2 is inactivated, the NDI of the transport block 1 indicates whether the data transmitted through the activated transport block 1 is new data or retransmitted data, The NDI field may be interpreted as a layer indicator (or antenna port indicator / reference signal location) for transport block 1. For example, if the logical value of the NDI of the deactivated transport block is a first value (0 or off), it indicates the first layer (layer X) or the first antenna port (antenna port X) (Layer Y) or a second antenna port (antenna port Y) when the logical value of the NDI is a second value (1 or on). Alternatively, the first value of the logical value of the NDI field may indicate 1 or on, the second value may indicate 0 or off, and may represent a corresponding relationship with the first and second layers, respectively. The terminal can distinguish which layer the channel information valid for itself is obtained through information obtained from the layer indicator. The interpretation of such a layer indicator can be set as shown in Table 23 below.

According to the new DCI format defined as shown in Table 22, the DCI format for dual layer beamforming and single layer beamforming can be set to have the same size, so that the dynamic mode adaptation of SU-MIMO and MU-MIMO, A dynamic rank adaptation of rank 2 can be implemented.

Next, another embodiment of a new DCI format that satisfies the above-mentioned consideration with reference to Table 24 will be described. Descriptions of portions common to Table 20 in the DCI format shown in Table 24 are omitted for brevity.

In the DCI format of Table 24, unlike the conventional DCI format 2A, the 'transport block to code word swap flag' may not be defined. Thus, if both codewords are activated, codeword 0 can be set to be mapped to transport block 1 and codeword 1 to be mapped to transport block 2.

On the other hand, when one transport block is activated and another transport block is inactivated, the activated transport block can be mapped to codeword 0 as shown in Table 2 above.

In the DCI format of Table 24, when the MCS index value of the transport block is set to 0 (or the MCS index value is 0 and the RV value is 1) to indicate that one transport block is activated and the other transport block is deactivated, The UE can implicitly recognize that it is a single layer beamforming transmission.

The new data indicator (NDI) field for the deactivated transport block can be interpreted as a layer indicator of the activated transport block. For example, when the transport block 1 is activated and the transport block 2 is inactivated, the NDI of the transport block 1 indicates whether the data transmitted through the activated transport block 1 is new data or retransmitted data, The NDI field can be interpreted as a layer indicator (or antenna port indicator, reference signal position) for transport block 1. For example, if the logical value of the NDI of the deactivated transport block is a first value (0 or off), it indicates the first layer (layer X) or the first antenna port (antenna port X) (Layer Y) or a second antenna port (antenna port Y) when the logical value of the NDI is a second value (1 or on). Alternatively, the first value of the logical value of the NDI field may indicate 1 or on, the second value may indicate 0 or off, and may represent a corresponding relationship with the first and second layers, respectively. The terminal can distinguish which layer the channel information valid for itself is obtained through information obtained from the layer indicator. The interpretation of such a layer indicator can be set as shown in Table 23 above.

On the other hand, in the new DCI format defined as Table 24, the precoding information field for four antenna ports can be configured as shown in Table 25 below.

Through the precoding information configured as shown in Table 25, the layer index to which the activated codeword is mapped and whether or not the RS overhead is changed can be notified. For example, the index of the layer group to which the activated codeword is mapped and how many layers in the layer group are used to indicate the transmission is used. In addition to this information, it may inform whether or not the RS overhead has changed. In order to inform the Release-9 UE of information about increased RS overhead, a predetermined bit value of the precoding information field may be used to inform information about increased RS overhead in the Rank 1 transmission.

According to the new DCI format defined as shown in Table 24, the DCI format for dual layer beamforming and single layer beamforming can be set to have the same size, and the dynamic mode adaptation of SU-MIMO and MU-MIMO, A dynamic rank adaptation of rank 2 can be implemented.

The new DCI format of Tables 20, 22, and 24 described above can be referred to as DCI format 2B or DCI format 2C (or another distinct DCI format name) that is distinguished from conventional DCI formats 2 and 2A, The antenna ports X and Y used may be referred to as antenna ports 7 and 8, which are distinct from the antenna ports defined in the existing LTE standard.

According to various embodiments of the present invention, in order to support dual layer beamforming, an existing DCI format may be newly analyzed, or a new DCI format may be defined differentiating from an existing DCI format to provide downlink control information to a terminal . In particular, it is possible to implicitly acquire, through the MCS field of the transport block, whether one of the two transport blocks is inactivated, without providing rank information through an explicit rank indicator in the dual layer beamforming. In addition, in transmission using a maximum of two layers, one bit of information is required to indicate a layer (antenna port) used for transmission. By using the NDI bit field for the inactive transport block among the two transport blocks, To the two terminals using a single layer.

Demodulation reference signal (DMRS) based multiuser-MIMO transmission scheme

Hereinafter, the proposal of the present invention for signal transmission and reception in a wireless communication system supporting multi-user-MIMO (MIMO) transmission will be described.

A MIMO system refers to a system that improves the transmission / reception efficiency of data by using multiple transmit antennas and multiple receive antennas. The MIMO technique includes a spatial diversity technique and a spatial multiplexing technique. The spatial diversity scheme can increase transmission reliability or diversity gain through diversity gain and is suitable for data transmission to a terminal moving at a high speed. Spatial multiplexing can increase the data rate without increasing the bandwidth of the system by transmitting different data at the same time.

In a MIMO system, each transmit antenna has an independent data channel. The transmit antenna may refer to a virtual antenna or a physical antenna. The receiver estimates a channel for each of the transmit antennas and receives data transmitted from each transmit antenna. Channel estimation is a process of recovering a received signal by compensating for distortion of a signal caused by fading. Here, fading refers to a phenomenon in which the strength of a signal is rapidly fluctuated due to a multi-path-time delay in a wireless communication system environment. For channel estimation, a reference signal known to both the transmitter and the receiver is required. The reference signal may also be referred to simply as a reference signal (RS) or as a pilot according to the applicable standard.

Among various downlink reference signals, a terminal-specific DMRS (Demodulation RS) for data demodulation is defined. The DMRS may be represented by a dedicated reference signal (DRS) as described above. A UE-specific DMRS can be used for multiuser-MIMO (MU-MIMO) transmission. Each UE can perform MU-MIMO operation without interference with other UEs using channel information obtained through precoding-based DMRS.

In the MU-MIMO transmission supporting multiple layers, the overhead of the DMRS and the position on the resource block may vary depending on the transmission rank. In a case where each terminal operating in the MU-MIMO operation does not know the existence of another terminal operating in the MU-MIMO operation, the location on the resource block to which the DMRS for the other terminal is allocated is allocated for data transmission to the terminal So that a malfunction may be caused in data demodulation. Accordingly, the present invention proposes a method of supporting each terminal to operate correctly in MU-MIMO transmission supporting multiple layers.

7 is a diagram for explaining patterns of a common reference signal (CRS) and a dedicated reference signal (DRS) in a 3GPP LTE system (for example, release-8). The common reference signal (CRS) may be referred to as a cell-specific reference signal, and the dedicated reference signal may be referred to as a UE-specific reference signal.

7 is a view for explaining a resource element to which a common reference signal and a dedicated reference signal in a general CP case are mapped. In Fig. 7, the horizontal axis represents time domain (OFDM symbol unit) and the vertical axis represents frequency domain (subcarrier unit). With respect to the reference signal pattern, in the case of a general CP, 14 OFDM symbols in the time domain and 12 subcarriers in the frequency domain can be the basic unit of the resource block. In the case of the extended CP, 12 OFDM symbols and 12 subcarriers can be the basic unit of the resource block for the reference signal pattern. The smallest rectangular area in the time-frequency domain shown in FIG. 7 is an area corresponding to one OFDM symbol in the time domain and one subcarrier in the frequency domain.

In Fig. 7, Rp indicates a resource element used for transmission of a reference signal on a p-th antenna port. For example, R0 to R3 represent resource elements to which common reference signals transmitted from the 0th to 3rd antenna ports are mapped, and R5 represents resource elements to which a dedicated reference signal transmitted from the 5th antenna port is mapped. The common reference signal transmitted at the zeroth and first antenna ports is transmitted at six subcarrier intervals (one antenna port reference) on the 0th, 4th, 7th and 11th OFDM symbols. The common reference signals transmitted at the second and third antenna ports are transmitted on the first and eighth OFDM symbols at six subcarrier intervals (one antenna port basis). The dedicated reference signal is transmitted at four subcarrier intervals on the third, sixth, ninth, and twelfth OFDM symbols of each subframe. Therefore, twelve dedicated reference signals are transmitted within two consecutive resource blocks (resource block pairs) in one subframe in time.

A common reference signal (CRS) (or a cell-specific reference signal) is used for estimating a channel of a physical antenna end, and is a reference signal transmitted to all UEs (UEs) in the cell. The channel information estimated by the UE through the common reference signal may be transmitted using a single antenna transmission, a transmit diversity, a closed-loop spatial multiplexing, an open-loop spatial multiplexing and can be used for demodulating data transmitted by a transmission technique such as multi-user MIMO (MU-MIMO), and also for measuring a channel and reporting it to a base station . In order to improve the channel estimation performance through the common reference signal, it is possible to shift the position of the common reference signal in each subframe for each cell by shifting. For example, when the reference signal is located for every three subcarriers, some cells may be arranged at a subcarrier interval of 3k and the other cells may be arranged at a subcarrier interval of 3k + 1.

The dedicated reference signal DRS (or the terminal-specific reference signal) is a reference signal used for data demodulation. In this respect, the dedicated reference signal may be referred to as a demodulation reference signal (DMRS). When a UE receives a reference signal by using a precoding weight used for a specific UE in a multi-antenna transmission as it is for a reference signal, an equalization channel, in which a precoding weight transmitted from each transmission antenna and a transmission channel are combined, . Also, the dedicated reference signal is required to be orthogonal between the transmission layers.

Existing 3GPP LTE systems (e.g., 3GPP LTE Release-8 systems) support transmission of up to 4 transmit antennas and include cell-specific reference signals to support a single transmit antenna, 2 transmit antennas, 4 transmit antennas, and rank 1 A terminal-specific reference signal for beamforming is defined. On the other hand, in the 3GPP LTE Release-9 system, one terminal can receive the transmission of the maximum rank 2.

On the other hand, high-order MIMO, multi-cell transmission, and advanced multi-user-MIMO are considered in the LTE-A (Advanced) system (3GPP LTE Release-10 and its subsequent standards) . Accordingly, a MIMO scheme that performs maximum rank 8 transmission for one UE can be applied. The LTE-A system considers data demodulation based on a dedicated reference signal in order to support an efficient reference signal operation and an improved transmission scheme. As described above, the dedicated reference signal based data demodulation means that, for example, when the terminal receives the downlink data from the base station, channel information for demodulating the downlink data is obtained from the dedicated reference signal. Also, it may be preferable that the dedicated reference signal is set by the base station such that the downlink transmission exists only in the scheduled resource blocks and layers. For example, the transmission of the maximum rank 8 based on the dedicated reference signal can be described as transmitting up to eight different dedicated reference signals multiplexed with the data for the terminal.

The dedicated reference signals for the respective layers can be multiplexed and arranged in disposing the dedicated reference signals for supporting the maximum rank 8 transmission introduced in the LTE-A system on the radio resources. Time Division Multiplexing (TDM) means placing dedicated reference signals for two or more layers on different time resources (e.g., OFDM symbols). Frequency Division Multiplexing (FDM) means placing dedicated reference signals for two or more layers on different frequency resources (e.g., subcarriers). Code Division Multiplexing (CDM) means multiplexing dedicated reference signals for two or more layers arranged on the same radio resource using an orthogonal sequence (or orthogonal covering).

Hereinafter, the demodulation reference signal DMRS will be described in more detail. As described above, a design of a 3GPP LTE-A system supporting higher uplink / downlink transmission rates than 3GPP LTE systems is under discussion. In the 3GPP LTE-A system, the downlink MIMO transmission supports maximum rank 8, and data demodulation can be performed based on the terminal-specific DMRS. Accordingly, a design of a DMRS for supporting transmission of rank 1 to 8 is required. Also, the DMRS for rank 1 to 2 transmission of LTE-A can be used for the dual-layer beamforming of 3GPP LTE Release-9. Before describing the DMRS used in the 3GPP LTE-A downlink MIMO transmission, the DMRS used for the downlink MIMO transmission of the existing 3GPP LTE system (release-8 or release-9) will be described.

Downlink MIMO transmission was also supported in the 3GPP LTE system prior to the 3GPP LTE-A system. A downlink MIMO transmission in a 3GPP LTE Release-8 system may support a single layer beamforming based on a precoded DMRS (may be referred to as a dedicated reference signal (DRS) or a terminal-specific reference signal) . In the case of downlink transmission using the precoded DMRS, the precoding weight is included in the channel information estimated by the receiver through the precoded DMRS, so that the transmitter can transmit the precoding weight information separately You do not need to tell. As an advanced form of such a single layer beamforming technique, downlink MIMO transmission in a 3GPP LTE Release-9 system can support dual layer (or dual stream) beamforming. The dual layer beamforming technique is a MIMO transmission scheme that supports maximum rank 2 transmission based on precoded DMRS.

Hereinafter, a DMRS design and an embodiment for an LTE-A system will be described.

A precoded reference signal may be used for downlink MIMO transmission in the LTE-A system, and the use of the precoded reference signal may reduce the reference signal overhead. Since the DMRS is precoded by the same precoder as the precoder applied to the data, the precoding matrix for the UE is transparent. Therefore, it is only required to transmit the DMRS corresponding to the layer, and it is not necessary to transmit separate precoding information.

DMRS overhead will be described. The DMRS overhead can be defined as the number of resource elements (RE) used for the DMRS per resource block in each transmission rank (e.g., one subframe in time × 12 subcarrier sizes on frequency) have.

For Rank 1 transmission, 12 REs in one resource block may be used for DMRS. This is the same as the overhead of DMRS (antenna port index 5) in 3GPP LTE Release-8.

For transmissions of rank 2 or higher, up to 24 REs in one resource block may be used for the DMRS. In case of transmission of rank 2 or higher, the same RE per antenna port in each rank can be used for DMRS.

Also, the same DMRS pattern can be used irrespective of the subframe type (TDD or FDD scheme). If the same DMRS pattern is used regardless of the subframe type, the complexity of the terminal operation can be reduced.

The details of the DMRS design for the LTE-A system are discussed below in terms of transmission mode independence, rank independence, subframe independence, and DMRS power boosting.

A terminal-specific precoded DMRS is supported for up to 8-layer transmissions in an LTE-A system, achieving high spectral efficiency (or bandwidth efficiency) requirements. Since the DMRS is defined as a UE-specific, it is first necessary to decide whether the DMRS should be optimized for each transmission mode or whether the same DMRS is used regardless of the transmission mode. In terms of the complexity of the terminal operation, a unified DMRS capable of performing the same demodulation operation regardless of the transmission mode will be more advantageous. Also, considering joint optimization of single user-MIMO (SU-MIMO), multiuser-MIMO (MU-MIMO) and cooperative multi-point (CoMP) Use of the same DMRS irrespective of an advantage may be advantageous in that it allows flexible and flexible scheduling among the various transmission modes. Therefore, it may be desirable to use the same DMRS pattern regardless of the transmission mode, unless it has a significant effect on performance.

It may be advantageous to use the same DMRS pattern regardless of rank in that the terminal can perform the same demodulation process in different transmission modes such as SU-MIMO, MU-MIMO and CoMP transmission and reception techniques. Here, using the same DMRS pattern irrespective of the rank means that the DMRS pattern (e.g., time-frequency position and code) for each layer is the same in all ranks. For example, the channel corresponding to layer index 1 can be estimated by the same channel estimator regardless of rank. In other words, using the same DMRS pattern regardless of rank means that the lower ranked DMRS pattern is a subset of the higher rank DMRS pattern. If the same DMRS pattern is used irrespective of rank, the terminal can perform data demodulation in the same operation in all transmission modes, so that the complexity of the terminal design can be reduced. Thus, it may be desirable to use a fixed DMRS pattern for each layer, regardless of rank.

In order to use one DMRS pattern regardless of the subframe type (FDD or TDD scheme) and to maintain the commonality in the FDD scheme and the TDD scheme, it is necessary to appropriately determine the position of the OFDM symbol used for DMRS transmission. Specifically, an OFDM symbol used as a guard period for a repeater backhaul link (link between a base station and a repeater), a last OFDM symbol used for a synchronization channel transmission in a TDD scheme, and the like are not used for DMRS transmission . In addition, an OFDM symbol including a cell-specific reference signal (or a common reference signal) defined in 3GPP LTE Release-8 can be also not used for DMRS transmission. This means that when power boosting of the cell-specific reference signal is used (reference signal power boosting means to draw power from an RE other than the RE allocated for the reference signal among the REs of one OFDM symbol) , The DMRS transmission power is lowered when the DMRS is transmitted on the same OFDM symbol to which the cell-specific reference signal is transmitted, and the demodulation performance is degraded. Therefore, it may be desirable to set the DMRS not to be transmitted in the OFDM symbol to which the guard interval of the cell-specific reference signal and the repeater backhaul subframe is allocated.

As described above, the DMRS overhead can be defined as 12 REs in one resource block for rank 1 transmissions and up to 24 REs in higher ranks. However, the DMRS transmission power must also be considered as the DMRS overhead. In the case of multiplexing DMRSs for a plurality of layers in a code division multiplexing (CDM) scheme, the DMRS transmission power is shared by a plurality of layers, so that the channel estimation performance can be lowered as the number of layers increases. Therefore, DMRS power boosting may be considered.

Considering these points, we propose several methods that can be used as DMRS patterns. As described above, in order to reduce complexity of the terminal operation and provide flexibility, it is possible to consider multiplexing the DMRS for the multi-layer by the CDM method.

Patterns-1 to -4 in FIGS. 8 and 9 correspond to candidates of CDRS-based DMRS patterns for supporting a high rank.

To allow a fixed DMRS pattern for each layer to be set independently of the rank, the CDM multiplexing can be applied only within the CDM-group including twelve REs. In FIGS. 8 and 9, 'C' and 'D' represent CDM-groups capable of multiplexing a maximum of four layers. The DMRS patterns shown in FIGS. 8 and 9 can all satisfy the above-described transmission mode independent and rank independent DMRS characteristics.

Typically, the DMRS pattern in Fig. 8 (a) will be described. The twelve REs labeled 'C' form one CDM-group. Four layers in one CDM-group can be multiplexed in the CDM scheme using Walsh covering. In other words, the DMRSs for the four layers are all placed on the same RE, and the DMRS for each layer can be distinguished (or identified) using CDM resources. The orthogonal cover of (1, 1, 1, 1) is multiplied with respect to the first layer, the orthogonal cover of (1, -1, 1, -1) is multiplied with respect to the second layer, 1, -1, -1) -1 is multiplied by the orthogonal cover of (1, -1, -1, -1) for the fourth layer. Or, if the DMRS for a number of layers equal to or less than 3, for example, are multiplexed, any three or less of the four orthogonal covers of the four different orthogonal covers may be selectively used. For example, if the DMRS for two layers is multiplexed, two of the four different orthogonal covers (e.g., (1, 1, 1, 1) and (1, 1)) can be used to distinguish (or identify) two DMRSs.

In the DMRS patterns of FIGS. 8 and 9, the DMRS overhead may vary depending on the transmission rank. As shown in FIGS. 8 and 9, two CDM-groups are used to support a maximum of eight layers, and each CDM-group can support up to four layers. Thus, the DMRS overhead can be defined differently depending on the number of CDM-groups. In this regard, two approaches can be considered.

First, in the case of rank 1 and rank 2, DMRS overheads of 12 REs are respectively provided, and in the case of rank 3 through 8, DMRS overheads of 24 REs can be set respectively. In the case of this DMRS overhead setting, rank 1 and rank 2 can be defined in one CDM-group, and two CDM-groups can be used from rank 3. Therefore, since a large amount of DMRS is used in the case of rank 3 or higher, robustness against mobility of the terminal can be increased, so that good performance for a low rank can be assured. However, in the case of Rank 3 and 4, the RS overhead may be too much.

Or, in the case of rank 1 to 4, DMRS overhead of 12 REs may be provided, and in the case of rank 5 to 8, each DMRS overhead of 24 REs may be set. In the case of this DMRS overhead setup, the RS overhead can be lowered compared to the scheme described above in terms of rank 3 and 4, since up to rank 4 can be defined in one CDM-group. However, in a situation of a high Doppler frequency, the channel estimation performance may be lower than the above-mentioned scheme.

In the above-mentioned two methods of setting the DMRS overhead, since the channel estimation performance and the RS overhead are in a trade-off relationship with each other, it is necessary to set the proper DMRS overhead considering this.

Hereinafter, the multiuser-MIMO (MU-MIMO) transmission scheme will be described in more detail. As described above, in order to operate the MU-MIMO defined in the 3GPP LTE (e.g., Release-8) system, each UE acquires channel information obtained through a cell- It is possible to perform data demodulation using one precoding weight information. When the MU-MIMO operates in the 3GPP LTE Release-9 and LTE-A systems that are designed to support the multi-layer, the base station does not need to inform each terminal of the precoding weight, MU-MIMO can be operated without multi-user interference using the acquired channel information. Here, for proper operation of the UE, it is necessary to indicate which layer of the multi-layer channel information obtained from the DMRS is for a specific UE. Hereinafter, the MU-MIMO design scheme for 3GPP LTE Release-9 and LTE-A systems will be described.

In the 3GPP LTE Release-9 system, a single layer beamforming defined in the 3GPP LTE Release-8 system can support the extended type of dual layer beamforming using a terminal-specific precoded DMRS. Accordingly, up to two layers can be supported, so SU-MIMO using precoded DMRS can be supported. The SU-MIMO scheme using precoded DMRS can provide better performance than SU-MIMO scheme based on codebook since the precoder can be optimized in the base station in a transparent manner to the UE. In addition, it may be required to support MU-MIMO in order to provide higher system throughput in 3GPP LTE Release-9 systems, which may extend the operating range of the dual layer beamforming from SU-MIMO to MU-MIMO .

For the MU-MIMO scheme based on the dual layer beamforming in the 3GPP LTE Release-9 system, it is determined whether to support MU-MIMO in the dual layer beamforming, orthogonal DMRS or non-orthogonal DMRS, interference cancellation / suppression, minimization of impact on existing standard documents, and power sharing indicators. Hereinafter, the above considerations will be described in detail. The advantages of MU-MIMO optimization using precoded multi-layer DMRS are also discussed.

In the 3GPP LTE Release-8 system, since the MU-MIMO scheme based on the SDMA (Spatial Division Multiple Access) using the precoded DMRS is supported without information on the interference channel, the system performance is relatively low, -channel interference could not be canceled or suppressed. Therefore, the performance of the system is limited depending on the antenna configuration and the scheduler. In order to enhance the MU-MIMO scheme in 3GPP LTE Release-9, it may be desirable to provide better system performance and robustness by allowing interference cancellation / suppression on the terminal side (unless there is a significant impact on existing standard documents) have.

In supporting single user dual layer beamforming, it may be considered to use orthogonal DMRS to support better rank 2 transmission. Thus, if performance gain can be achieved, it may be desirable to utilize the orthogonal DMRS already designed for MU-MIMO as much as possible. In order to improve the MU-MIMO performance, it is considered to increase signal-to-interference-plus-noise ratio (SINR) at the UE side by canceling and / or suppressing co- . Therefore, it may be desirable to use an orthogonal DMRS that allows interference channel estimation for better performance.

As described above, in the SDMA-based MU-MIMO scheme in the 3GPP LTE Release-8 system, since the co-channel interference can not be canceled and / or suppressed on the terminal side, its performance is limited to a certain level. In order to allow interference cancellation, scheduling information such as modulation and coding scheme (MCS), channel and rank for other UEs co-scheduled in the same physical resource block (PRB) are shared There is a need, and excessive signaling overhead can occur. Also, the signaling overhead for interference cancellation may become more severe if the co-scheduled terminals are not allocated to the same PRB. On the other hand, since interference suppression requires only interference channel information, interference suppression may be more appropriate than interference cancellation as an enhancement technique for MU-MIMO in the 3GPP LTE Release-9 system. If the UE knows the presence of another UE interfering with the UE and the DMRS index associated with the UE's transport block demodulation, the interference channel can be estimated using the orthogonal DMRS. Therefore, interference suppression is supported in 3GPP LTE Release-9 dual layer MU-MIMO, and it may be desirable to provide relevant control information (DMRS index and co-scheduling indicator for that terminal) for interference suppression. However, it is necessary to consider the influence on the existing standard document as to whether the control information explicitly instructed to the terminal is necessary.

Of the control information associated with interference suppression, the signaling overhead can be increased if explicitly a co-scheduling indicator is sent in each scheduled PRB to avoid scheduling restrictions. In this situation, CDM-based DMRS can be a solution to this problem. That is, in the case of using the CDM-based DMRS, the UE can detect co-channel interference with the orthogonal DMRS using energy detection in each scheduled PRB without any signaling, and if there are other interfering terminals Since it is possible to suppress the interference signal in each scheduled PRB. Therefore, the DMRS indicator using the CDM-based orthogonal DMRS can minimize the impact of the standard document to support MU-MIMO. If a similar approach is applied for SU-MIMO Rank 1 transmission, a common PDCCH may be used for both SU-MIMO and MU-MIMO.

In the 3GPP LTE Release-8 system, since the common reference signal (CRS) is provided cell-specific, power sharing information may be required for demodulation if Quadrature Amplitude Modulation (QAM) based modulation is used. However, when a terminal-specific reference signal is used (since the terminal-specific reference signal is not shared with other terminals), power sharing information is implicitly included in the reference signal. In this case, the UE can estimate that the RE to which the data is transmitted and the RE to which the UE-specific reference signal is transmitted have the same power level. Therefore, whether or not to support DMRS power boosting can be considered only in terms of channel estimation performance enhancement, which is the same in the case of SU-MIMO. Therefore, the power sharing indicator may not be specified for MU-MIMO support.

Considering the DMRS-based MIMO transmission, as described above, the overhead of the DMRS can be set differently according to the transmission rank. For example, the DMRS for supporting rank 1 to 2 may be designed to maintain a constant overhead, and to have an increased overhead when supporting rank 3 or higher. Or the DMRSs from rank 1 to rank 4 may be designed to maintain a certain level of overhead and have an increased overhead for rank 5 or higher.

In the case of maintaining the overhead of the DMRS of rank 1 to 2 at a constant level, the overhead of the DMRS can be kept constant in the data transmission through the DMRS-based dual layer beamforming of the 3GPP LTE Release-9 system. When supporting MU-MIMO in the 3GPP LTE Release-9 system, up to two terminals can be multiplexed (each terminal performs a single layer transmission), and in terms of DMRS-based MIMO transmission, the base station uses a DMRS The DMRS overhead and the position of the DMRS on the resource block can be always maintained even when the MU-MIMO is performed. The base station instructs a terminal that performs MU-MIMO transmission to indicate a specific layer of two layers so that the terminal can acquire an orthogonal channel. In the case where there is no overhead of the DMRS or a location on the resource block of the DMRS, the MU-MIMO can be operated using a layer indicator.

On the other hand, if a maximum rank supporting MU-MIMO is determined in a range exceeding the reference rank for a rank that is a reference for which the position on the DMRS overhead or the DMRS resource block is changed, the data of the terminal operating in the MU- Significant problems with demodulation can occur. For example, in the case of the rank 1 to 2, the DMRS is multiplexed using the CDM-group 'C' of FIG. 8A (that is, 12 REs are used in one resource block) The DMRS can be multiplexed using all of the CDM-groups 'C' and 'D' of FIG. 8 (a) (ie, using 24 REs in one resource block). In this case, it may be assumed that the DMRS is additionally disposed at a position on the resource block of the DMRS supporting ranks 1 to 2 for transmission of rank 3 or more. At this time, when it is assumed that three terminals, each receiving a single layer transmission, are multiplexed to perform an MU-MIMO operation, the base station transmits data using the DMRS for supporting Rank 3. The terminals (the first and second terminals) that are allocated the first layer and the second layer acquire channels from rank 1 to 2 DMRS positions, and the terminal (third terminal) that is allocated the third layer receives the rank 3 DMRS To obtain the channel from the further allocated DMRS location. When the layer indicator indicates the layer allocated to each UE as described above, the terminals (first and second terminals) allocated to the first layer / second layer may not recognize the existence of the third layer have. At this time, since the REs of the added DMRS positions can be mistaken for being used for data transmission other than the DMRS, the first and second terminals may cause serious problems in data demodulation at the first and second terminals have. Therefore, when the overhead of the DMRS or the position on the resource block changes according to the rank, it is necessary to inform the terminal operating in MU-MIMO of the maximum rank.

Embodiment 4

Hereinafter, embodiments of the present invention for DMRS-based MU-MIMO transmission will be described in detail.

In the present invention, it is proposed to use a rank indicator to inform a terminal operating in MU-MIMO of the maximum rank. In SU-MIMO, the rank indicator may indicate the rank currently being transmitted. On the other hand, in MU-MIMO, the rank indicator may be used by multiple users to represent the multiplexed overall rank, or may be used to indicate the number of layers allocated for a particular terminal.

More specifically, the rank indicator may be used to indicate the total transmission rank of the multiplexed terminals for MU-MIMO. For example, when there are M (M? 2) terminals transmitting a rank N (N? 1), the base station transmits a total of K (K = N * M) ranks. At this time, the base station can notify that the DMRS pattern is being used for supporting the rank K, which is being transmitted to the rank of the total K through the rank indicator, and the terminal recognizes that the DMRS for supporting the rank K is used . According to this scheme, even when the DMRS pattern or the overhead is changed according to the transmission rank, the terminal can definitely distinguish (or identify) the RE used for the DMRS and the RE used for the data. The terminal can acquire channels of K layers through the DMRS of rank K. The terminal can distinguish (or identify) which layer the valid channel information is by acquiring from the information obtained from the layer indicator.

For example, assuming that a total transmission rank is 3, one terminal supports rank 1 transmission. It is assumed that the base station transmits DMRS through 12 REs in one RB up to the total transmission rank 2 and transmits DMRSs through 24 REs in one RB in rank 3 or higher. If the information on the aggregate transmission rank is not known to the UE operating in the MU-MIMO operation, then the UE receives the DMRS location for the Rank 1 transmission (12 RE locations in one RB, e.g., Quot; C &quot; position of &quot; C &quot;). Accordingly, the UE transmits data at the RE position (the 12 RE positions in one RB, for example, the position of 'D' in FIG. 8A) in which the DMRS for the other terminal performing the MU- The data is demodulated. Therefore, there arises a problem that data can not be correctly demodulated. On the other hand, when information on the total transmission rank is known to the UE as described above, the UE can know the RE location to which a valid DMRS is allocated to other UEs in addition to the DMRS location valid for itself, It can be seen that the data is not transmitted. Therefore, the UE can reliably discriminate between the RE to which the DMRS is transmitted and the RE to which the data is allocated, and can correctly demodulate the data.

If only the maximum rank 1 transmission is allowed for each UE operating in the MU-MIMO operation, the UE can acquire only the channel of the layer indicated by the layer indicator.

On the other hand, when transmission of the maximum rank P (P? 2) is allowed for each terminal operating in the MU-MIMO operation and multiple codeword transmission is allowed for each terminal, the terminal increments from the layer indicated by the layer indicator It is possible to acquire the channels of the P layers according to the order. For example, if data transfer using a maximum of two layers is allowed, the layer indicated by the layer indicator (e.g., layer index 1) and a layer in an order of increasing order (e.g., layer index 2 &Lt; / RTI &gt; On the other hand, when one-layer transmission is performed in a situation where transmission of a maximum of two layers is allowed, the terminal may recognize that the transmission is Rank 1 transmission through other information. For example, from the MCS information of each codeword, whether the codeword is activated or not can be acquired implicitly, and the number of transmission layers can also be obtained through this. For example, the UE can recognize the transmission as Rank 2 transmission when all two codewords are activated, and as Rank 1 transmission if only one codeword is activated.

On the other hand, when transmission of the maximum rank P (P? 2) is permitted for each terminal operating in the MU-MIMO operation and a single codeword transmission is allowed for each terminal, the terminal increments from the layer indicated by the layer indicator It is possible to acquire the channels of the P layers according to the order.

In summary, the entire transmission rank, information on layers available to each of the terminals, and rank information about each of the terminals can be provided to terminals operating in the MU-MIMO through the same resource, It is possible to reliably distinguish (or identify) the location of the DMRS and the data on the channel and acquire valid channel information.

On the other hand, in the various embodiments of the present invention described above, the following settings may be applied with respect to the rank indicator.

First, it is possible to set up to 8 ranks using a 3-bit rank indicator.

Secondly, it is possible to set up to 4 ranks to indicate the total rank multiplexed for MU-MIMO using 2-bit rank indicator.

Third, one bit indicator may be used to indicate that the DMRS overhead or location is changed without setting a rank indicator. The one-bit indicator can indicate whether the DMRS overhead is increased (or additional DMRS position) on / off.

In supporting the MU-MIMO operation as described above, a codeword-to-layer mapping relationship needs to be newly defined in terms of the base station and the terminal. This will be explained with reference to Tables 26 to 37 below

Tables 26 to 31 below show a case where a maximum rank P (P &gt; = 2) transmission is allowed for each terminal operating in the MU-MIMO operation and transmission of multiple codewords (maximum 2 CW) is allowed for each terminal Represents a codeword-to-layer mapping for the &lt; RTI ID = 0.0 &gt; Tables 26 to 29 show codeword-to-layer mappings for the cases of the maximum transmission ranks 1, 2, 3 and 4, respectively, from the viewpoint of the base station. Tables 30 and 31 show codeword-to-layer mappings for the cases of maximum receive rank 1 and 2, respectively, from a terminal perspective.

Tables 32 to 37 below show a case where a maximum rank P (P &gt; = 2) transmission is allowed for each terminal operating in the MU-MIMO operation and transmission of a single codeword (1 CW) Code word-to-layer mapping. Tables 32 to 35 show codeword-to-layer mappings for the cases of maximum transmission ranks 1, 2, 3 and 4, respectively, from the viewpoint of the base station. Tables 36 and 37 show codeword-to-layer mappings for the case of the maximum receive ranks 1 and 2, respectively, from a terminal perspective.

The codeword-to-layer mapping relationship in the case of the maximum reception rank 2 in terms of the terminals shown in Tables 26 and 37 can be used not only for the initial transmission in the MU-MIMO transmission but also in the retransmission.

Control information that simultaneously supports SU-MIMO and MU-MIMO

In various embodiments of the present invention described above, a method of indicating a layer to be read for data demodulation among DMRS used for transmission in a system supporting dual layer beamforming based on DMRS has been proposed. In the case of performing the dual layer beamforming transmission, the DMRS can be transmitted through 12 REs in one resource block, and the DMRS for each layer can be transmitted using two orthogonal cover codes (OCCs) (Or identified) from each other. That is, the two OCCs can be used as orthogonal resources for distinguishing (or identifying) the DMRS. Also, when performing the MU-MIMO transmission using the dual layer, the NDI bit of the inactivated codeword can be used as an indication of a valid DMRS among the transmitted DMRS resources.

Referring to FIG. 8 (a) again, the DMRS pattern will be described. In FIG. 8 (a), DMRS can be mapped onto 24 REs in one resource block. In FIG. 8 (a), 12 resources corresponding to the CDM group 'C' and 12 resources corresponding to the CDM group 'D' are distinguished (or identified) in the time / frequency domain. And each of the 'C' and 'D' groups can distinguish (or identify) four different DMRSs using orthogonal code resources. In FIG. 8 (a), four orthogonal Walsh codes are used to distinguish (or identify) four different DMRSs.

Alternatively, one DMRS CDM group may be divided into two subgroups. The two subgroups may be quasi-orthogonal to each other. Two layers (or antenna ports) can be distinguished (or identified) using a fully orthogonal sequence within a sub-group. Two completely orthogonal sequences may be, for example, {1, 1, 1, 1} and {1, -1, 1, -1}. In other words, the DMRSs that are distinguished (or identified) by two completely orthogonal sequences can be referred to as DMRSs for different antenna ports (e.g., {1, 1, 1 , 1} code resources are used and {1, -1, 1, -1} are used for antenna port Y), two DMRSs are separated (or separated) using quasi-orthogonal code resources for each antenna port (For example, there are two DMRSs distinguished (or identified) with respect to the antenna port X, and there are two DMRSs separated (or identified) with respect to the antenna port Y) . In summary, a total of four different DMRSs can be distinguished (or identified) by code resources on one DMRS CDM group (e.g., 'C') of twelve REs. On the other hand, the CDM groups 'C' and 'D' may be referred to as group 1 and group 2. As a resource for discriminating (or identifying) the DMRS, four orthogonal resources per two groups and groups can be used, so that a total of eight orthogonal resources can be secured.

It is assumed that 12 REs are used for DMRS transmission in Rank 1 and 2, and 24 REs are used for DMRS transmission in rank 3 or higher. Up to rank 2, only one group (i.e., 'C') is used for DMRS transmissions, while two or more groups (i.e., 'C' and 'D') are used for DMRS transmissions above rank 3. For example, in the case of transmitting the DMRS for each of the first to fourth layers in the rank 4 transmission, the DMRS for any two layers (e.g., the first and second layers) And the DMRS for the remaining two layers (e.g., the third and fourth layers) may be mapped to another group (e.g., 'C' 'D') and may be separated (or identified) into OCCs.

In the case of MU-MIMO transmission using a maximum of four layers from the viewpoint of a transmitting end, a DMRS capable of distinguishing (or identifying) four layers is used. At this time, it is necessary to acquire information about a layer corresponding to each layer in the respective receiving stations. According to the method of indicating the layer using the NDI bit (1 bit) of the inactivated codeword as described above, it is possible to support only two terminals using a single layer. Therefore, Do.

First, it may be considered to define a CDM group indication bit. For example, a 1-bit indicator may be used to inform the terminal of the group to which the corresponding layer belongs among the first and second CDM groups (for example, 'C' or 'D' in FIG. 8 . One group consists of twelve REs, and up to four DMRSs can be multiplexed (i.e., separated) by the CDM scheme and transmitted through each group. In the case of MU-MIMO transmission using up to four layers as described above, two DMRSs in one group can be multiplexed by the CDM scheme using two orthogonal codes. When the group is determined through the 1-bit group indicator, one of the two orthogonal codes can be determined using the NDI (1 bit) of the deactivated codeword. Further, when it is determined which group is used by the 1-bit group indicator, if both codewords are activated, it is not necessary to indicate what the orthogonal code is because it uses both of the two orthogonal codes. Thus, by defining a 1-bit group indicator, a signaling scheme capable of effectively supporting MU-MIMO transmission with a maximum of 4 layers can be provided.

Hereinafter, a description will be given of a method capable of supporting both SU-MIMO and MU-MIMO transmission using the same control information format in a system using two codewords and supporting transmission of a maximum rank N (N? 8) do. First of all, what can be included in such control information will be discussed, and a concrete method of configuring a control information format will be proposed.

(1) As control information for MIMO transmission, rank and precoding information are basically required.

(2) The rank information means the number of virtual antennas (or streams or layers) used for transmission. When the data is demodulated using the MIMO receiver, the rank information determines the number of layers to be demodulated based on the rank information . The rank information from a single user viewpoint can be expressed as &quot; the number of layers to be received by one user &quot;. In the case where MU-MIMO is applied, the transmitting end can transmit data to a plurality of receiving ends (a plurality of users) using a multi-layer. Therefore, from a multi-user viewpoint (or from the viewpoint of a transmitting end of an MU-MIMO transmission), rank information can be expressed as 'the number of all layers used in transmission'.

(3) Precoding information refers to information on the precoding weight used by the transmitter in signal transmission. In order to reduce the size of the indicator bit for the precoding weight, a method of preliminarily defining a precoding weight in the form of a codebook and reporting an index of a codebook corresponding to the precoding information used for transmission may be considered . The receiving end can perform data demodulation by combining information on the precoding weight indicated by the transmitting end and channel information obtained through the reference signal. On the other hand, the dedicated reference signal (or demodulation reference signal) is precoded by the same precoder as the data to be transmitted. Thus, if a dedicated reference signal for a user is used, the information on the precoding weight may not be signaled separately.

(4) In a system using a dedicated reference signal, only the rank information can be basically indicated for MIMO transmission. For example, in a maximum rank two transmission system, a rank indicator of one bit is required for rank indication. The maximum rank 4 transmission system requires a 2-bit rank indicator, and the maximum rank 8 transmission system requires a 3-bit rank indicator.

(5) In multi-codeword (MCW) transmission, the following can be considered. A multi-antenna transmission can support both transmission using a single layer and transmission using multiple layers. When performing multi-layer transmission, different modulation and coding techniques (MCS) may be applied to each layer. In this way, transmission that applies multiple MCSs to multiple layers can be referred to as multi-codeword transmission. When applying each MCS to multiple layers, the signaling overhead may increase, so that some of the multiple layers (s) can be designed to have the same MCS. For example, in a system where two layers are transmitted, each layer may have a different MCS. In a system where three layers are transmitted, one layer is allocated an MCS for the layer, and the other two layers are allocated an MCS according to the channel conditions of the two layers. The two layers may be designed to have the same MCS. On the other hand, the bit indicating the MCS may include the MCS level and the code word deactivation information.

(6) In a system transmitting two codewords, when it is assumed that two MCS indicators are assigned to a control channel for transmission (each MCS indicator may include indication information for codeword deactivation), one When the MCS indicator indicates the deactivation of the codeword, the receiving end can recognize that the codeword is not transmitted but only the other codeword is transmitted. Also, if both MCS indicators indicate an MCS level, it can be seen that both codewords are transmitted at the receiving end.

(7) When performing multiple codeword (MCW) transmission in a system supporting maximum rank 2 transmission, an MCS indicator for each layer may be used. One bit can be assigned as an indicator for the rank to be transmitted. However, in the case of the maximum rank 2 transmission, whether the codeword is activated or not can be known whether the single-layer transmission or the two-layer transmission is performed without assigning an indicator for the transmission rank. When each codeword is transmitted through each layer, the transmission rank can be known depending on which codeword is active or inactive. In particular, in a system with two codewords, in the case of a maximum rank 2 transmission, only one codeword is activated in the rank 1 transmission, and both codewords are activated in the rank 2 transmission. Therefore, in a system in which multiple codewords are supported and each codeword is transmitted through each layer, the transmission rank information can be obtained through the information included in the MCS indicator, so that the information on the rank is not separately signaled It is possible.

(8) When MIMO transmission is performed using a dedicated reference signal (DRS or DMRS), the orthogonal resource (resource to be distinguished) for the reference signal is the same as the number of layers used for MIMO transmission. Orthogonal resources that discriminate (or identify) the reference signal may be code resources, frequency resources, and / or time resources. For example, in the case of a rank 2 transmission, two orthogonal resources are required for a dedicated reference signal. However, considering MU-MIMO, dedicated reference signal orthogonal resources as many as the number of layers to be transmitted to all of the multiple users are required. For example, in the case of transmitting Rank 2 to two users respectively, a total of four orthogonal resources are used for a dedicated reference signal.

(9) In a MU-MIMO system using a dedicated reference signal, it is necessary for a receiving terminal to demarcate a signal in order to distinguish (or identify) multiple users' reference signals. For example, two orthogonal resources are used when signals for two users transmitting Rank 1 transmission are simultaneously transmitted. If the order of two orthogonal resources is determined, each user is given an orthogonal resource Can be given.

If the DMRS group indication bits described above, the rank indication bits used for SU-MIMO transmission, and the rank indication bits indicating the entire layer used in the MU-MIMO transmission are all defined, clear control information for the MIMO transmission is provided The signaling overhead is greatly increased. In the present invention, an efficient control information signaling scheme capable of reducing the signaling overhead while simultaneously supporting SU-MIMO and MU-MIMO is proposed as follows.

Embodiment 5

The present embodiment is directed to a scheme for constructing control information indicating rank and layer used for transmission for rank 1 and rank 2 transmission and reporting transmission rank information only for transmission having rank 3 or higher.

For example, in the MU-MIMO transmission, it is assumed that a maximum of two layers can be received for each receiving terminal, and a maximum of four layers are transmitted in the transmitting terminal. In this case, an indication bit is required to identify (or identify) four layers for the terminals participating in the MU-MIMO. In the case of applying the Indication scheme for MIMO transmission described above, it is possible to provide the control information to recognize the A to D states of Table 38 at the receiving end.

Table 39 shows an example of codeword-to-layer mapping rules for transmission of up to 8 layers.

Considering the codeword-to-layer mapping rule as shown in Table 39, data is transmitted in rank 1, 2, 3, or 4 when one codeword is activated, and ranks 2 and 3 , 4, 5, 6, 7 or 8, respectively. Therefore, if the transmission rank is defined according to the number of activated codewords, it can be expressed as shown in Table 40.

Table 40 shows the contents of precoding information for supporting 8 antenna ports. Layer 1 through Layer 8 (s) in Table 40 represents the number of layers used to transmit the corresponding data from a single user viewpoint. As shown in Table 40, a minimum of 3 bits is required to indicate rank information. If three bits are used, four fields can be reserved if one codeword is activated, and one field can be reserved if two codewords are activated.

On the other hand, if a rank indicator is used for transmission up to rank 4, two bits can be used as the rank indicator. The 2-bit rank indicator can be configured as shown in Table 41. Table 41 shows the contents of precoding information for supporting four antenna ports.

As shown in Table 41, one field may be reserved if one codeword is activated, and one field may be reserved if two codewords are activated.

On the other hand, when a rank indicator is used for transmission up to rank 2, one bit can be used as a rank indicator. The 1-bit rank indicator can be configured as shown in Table 42. [ Table 42 shows the contents of precoding information for supporting two antenna ports.

As shown in Table 42, in the case of transmission on a two-antenna port, it can be recognized that one code word is activated when the one code word is activated, and that it is rank 2 transmission when two code words are activated. Therefore, it is possible to operate correctly without defining a separate bit for indicating the rank.

Next, a method of defining a layer indication in the precoding information field is proposed as follows.

MU-MIMO is applied in rank 1 and rank 2 transmission, and SU-MIMO is applied in rank 3 or higher transmission, the precoding information field for 8 antenna ports can be configured as shown in Table 43 below.

On the other hand, MIMO transmission of rank 2, 3 or 4 is possible when one codeword is activated. When one codeword is activated, it can indicate a group to which two layers are allocated in order to enable MU-MIMO transmission in Rank 2 transmission. In this case, the precoding information field for 8 antenna ports can be configured as shown in Table 44 below.

If the terminal demodulates data through the DMRS, it is assumed that the maximum number of REs is used for the DMRS. For example, when a DMRS CDM group 1 is indicated for a UE, data demodulation is performed in consideration of an RE location (for example, a DMRS CDM group 2) to which a DMRS for another UE is mapped in addition to RE for data and reference signals Can be performed. The information to be transmitted is calculated in consideration of the maximum number of REs of the DMRS, and the information can be encoded / decoded accordingly. For a terminal belonging to the DMRS CDM group 1, the number of REs for rank 1 or rank 2 transmissions (for example, when a total of 24 REs are used for DMRS transmissions, 12 &Lt; / RTI &gt; only REs are used).

On the other hand, when MU-MIMO is applied in the transmission of rank 1 and rank 2, and SU-MIMO is applied in transmission of rank 3 or higher, the precoding information field for four antenna ports can be configured as shown in Table 45 below .

On the other hand, when one codeword is activated, a group to which two layers are allocated can be informed in order to enable MU-MIMO transmission in Rank 2 transmission. In this case, the precoding information field for 4 antenna ports can be configured as shown in Table 46 below.

The precoding information field configured as shown in Tables 39 to 46 may be included in the downlink control information (DCI) format. Here, the precoding information field is used to indicate that the control information to be included in the DCI format proposed by the present invention reuses the precoding information field of the existing DCI format 2A. That is, the control information proposed in the present invention has a format similar to the format of the 'precoding information' included in the conventional DCI format 2A. As described above, the actual contents of the control information are the case where only one codeword is activated, (Or an antenna port) to which the data is to be transmitted. Thus, the name of the control information may be used differently. For example, the control information illustrated in Tables 39 to 46 includes control information indicating a transmission rank and a group to which a layer belongs in the DCI format of the modified DCI format of the existing DCI format 2A proposed in the present invention or the newly proposed DCI format May be included as information.

Embodiment 6

In the present embodiment, when rank 1 and rank 2 transmission are indicated with rank and layer used for transmission and only transmission rank information is reported with respect to transmission of rank 3 or higher, MU-MIMO is assigned to the same CDM group And the control information for the case where it is applied in the case of FIG. MU-MIMO is applied in the same CDM group means that a dedicated reference signal for one or more layers for multiple users is sent on the same CDM group (e.g., 'C' in FIG. 8 (a) .

For example, it can be assumed that a maximum of two layers can be received for each receiving end in a MU-MIMO transmission applied in the same CDM group, and a maximum of four layers are transmitted in a transmission end. In this case, an indication bit is required to identify (or identify) four layers for the terminals participating in the MU-MIMO. In the case of applying the Indication scheme for MIMO transmission as described above, it is possible to provide the control information so that the receiving end recognizes the states A to D of Table 47. [ Table 47 illustrates that MU-MIMO transmission is illustratively performed in group 1, but this is for any group and thus the present invention is not limited thereto.

Dedicated reference signals for four layers belonging to a predetermined group can be divided (or identified) into four orthogonal codes. The four orthogonal codes can be divided into two subgroups (for example, A-subgroup and B-subgroup as shown in Table 47). For example, one group may be divided into two subgroups, and the two subgroups may be quasi-orthogonal to each other. The two layers in one subgroup can be distinguished (or identified) by codes that are fully orthogonal to each other. The orthogonal code for each layer can be determined according to the antenna port mapping rule of the DMRS.

It is assumed that MU-MIMO is applied in rank 1 and rank 2 transmission, SU-MIMO is applied in transmission of rank 3 or higher, and MU-MIMO is performed in only one group (e.g., group 1). In this case, the number of REs used for the DMRS can be limited to 12. Accordingly, the precoding information field for 8 antenna ports can be configured as shown in Table 48 below.

On the other hand, MIMO transmission of rank 2, 3 or 4 is possible when one codeword is activated. When one codeword is activated, a subgroup assigned two layers may be informed to enable MU-MIMO transmission in Rank 2 transmission. In this case, considering that MU-MIMO is applied in a predetermined one group, the precoding information field for 8 antenna ports can be configured as shown in Table 49 below.

The terminal considers the number of REs for rank 1 or rank 2 transmissions (e.g., only 12 REs are used when performing a rank 1 or 2 transmission when a total of 24 REs are used for DMRS transmissions) To perform encoding / decoding.

On the other hand, considering that MU-MIMO is applied in Rank 1 and Rank 2 transmission, and SU-MIMO is applied in transmission of rank 3 or higher, considering that MU-MIMO is applied in a predetermined one group, Lt; / RTI &gt; may be configured as shown in Table 50 below. &Lt; tb &gt; &lt; TABLE &gt;

On the other hand, when one codeword is activated, a group to which two layers are allocated can be informed in order to enable MU-MIMO transmission in Rank 2 transmission. In this case, considering that MU-MIMO is applied in a predetermined group, the precoding information field for 4 antenna ports can be configured as shown in Table 51 below.

The precoding information field configured as shown in Tables 48 to 51 may be included in the downlink control information (DCI) format. Here, the precoding information field is used to indicate that the control information to be included in the DCI format proposed by the present invention reuses the precoding information field of the existing DCI format 2A. That is, the control information proposed in the present invention has a format similar to the format of the 'precoding information' included in the conventional DCI format 2A. As described above, the actual contents of the control information may include one code word transmission or two code word transmission And the sub-group to which the layer (or antenna port) to which data is transmitted belongs to the UE. Thus, the name of the control information may be used differently. For example, the control information illustrated in Tables 48 to 51 indicates the sub-group to which the transmission rank and the layer belong in the DCI format of the modified DCI format of the existing DCI format 2A proposed by the present invention or the newly proposed DCI format And may be included as control information.

When a group to which a MIMO transmission layer for a terminal belongs is indicated as in Embodiment 5 described above, layers can be distinguished (or identified) by using two OCCs in the group. When one codeword is transmitted, the antenna port, layer number or OCC information for the codeword being activated can be obtained through the NDI bits of the codeword being deactivated. When two codewords are activated, two OCC resources available in the group may be used.

Meanwhile, when the sub-group to which the MIMO transmission layer for the UE belongs is indicated as in the above-described Embodiment 6, the layers can be separated (or identified) by using two OCCs in the sub-group. When one codeword is transmitted, the antenna port, layer number or OCC information for the codeword being activated can be obtained through the NDI bits of the codeword being deactivated. When two codewords are activated, two OCC resources that can be used in a subgroup can be used.

A method of transmitting and receiving a downlink signal in a wireless communication system supporting MIMO transmission according to an embodiment of the present invention will be described with reference to FIG. A downlink transmission entity (e.g., a base station) in FIG. 10 can transmit downlink signals through eight transmission antennas, and a downlink reception entity (e.g., a terminal) can transmit downlink signals transmitted from a downlink transmission entity Signal can be received. Also, the downlink transmission entity may be a repeater for transmitting an access downlink signal to the terminal, and the downlink reception entity may be a repeater for receiving a backhaul downlink signal from the base station.

In step S1010, the downlink transmission entity may transmit the downlink control information. Accordingly, in step S1030, the downlink receiving entity can receive the downlink control information. The downlink control information may be information for scheduling downlink data transmitted on N (1? N? 8) layers. The downlink control information may be transmitted in the form of a PDCCH DCI format.

In step S1020, the downlink transmission entity may transmit downlink data and a terminal-specific reference signal (or DMRS) transmitted on N layers based on the downlink control information of step S1010. The downlink data and the UE-specific reference signal can be multiplexed and transmitted on the PDSCH. Accordingly, in step S1040, the downlink receiving entity can receive the downlink data and the UE-specific reference signal.

In step S1050, the downlink receiving entity may demodulate the downlink data transmitted on the N layers based on the UE-specific reference signal.

The downlink control information may include information for scheduling downlink MIMO transmission when only one codeword is active or when both codewords are activated. The downlink control information may include information indicating the number (N) of layers to which the activated codeword is mapped. When the downlink transmission entity is provided with 8 transmission antennas, 1? N? 8 may be used. Specifically, one to four layer transmission can be performed when only one code word is activated, and two to eight layer transmission can be performed when two code words are activated. Here, the number of layers may mean a rank. For example, the downlink control information may include control information such as Tables 40 to 44 or Tables 48 to 51.

The information indicating the number of layers in the downlink control information may also include information for a code identifying the terminal-specific reference signal, i.e. information for distinguishing terminal-specific reference signals transmitted at the same resource element location have. For example, as in the reference signal group 'C' of FIG. 8A, four different UE-specific reference signals transmitted at the same resource element position may be included in one reference signal group, The group may be divided into two subgroups according to information on a code for identifying a UE-specific reference signal, and one subgroup includes two UE-specific reference signals divided by an orthogonal code . For example, as shown in Table 48, the information indicating the number of layers may be composed of 3 bits. In the case where one codeword is mapped to one layer and two codewords are mapped to two layers Information indicating the sub-group to which the layer belongs (i.e., information on a code identifying the terminal-specific reference signal) may be included together. The downlink control information may further include information indicating an antenna port of the downlink MIMO transmission.

In the downlink signal transmission and reception method of the present invention described with reference to FIG. 10, the above-described aspects of various embodiments of the present invention (i.e., various DCI format configuration schemes proposed by the present invention) can be applied equally. For example, in the case of constructing the downlink control information (DCI) format for DMRS-based data transmission for each UE in a system supporting maximum rank 8 MIMO transmission, as described in the fifth and sixth embodiments , SU-MIMO, and MU-MIMO at the same time (i.e., using one DCI format). The control information includes information indicating a group (i.e., a reference signal position) to which a dedicated reference signal assigned to the terminal belongs, information indicating a transmission rank (number of layers) for the terminal, information indicating the total transmission rank, And information indicating a transport layer for the corresponding terminal. Here, the information indicating the transmission layer is information capable of distinguishing (or identifying) the dedicated reference signal for demodulating the data transmitted through the layer (or the antenna port) from the dedicated reference signal for the other layer. The above control information may be included in a DCI format 2A proposed in the present invention or in a new DCI format.

11 is a diagram showing a configuration of a preferred embodiment of a base station apparatus 1110 and a terminal apparatus 1120 according to the present invention.

11, a base station apparatus 1110 according to the present invention may include a receiving module 1111, a transmitting module 1112, a processor 1113, a memory 1114, and a plurality of antennas 1115. [ The plurality of antennas 1115 refers to a base station device supporting MIMO transmission / reception. The receiving module 1111 can receive various signals, data, and information on the uplink from the terminal. The transmission module 1112 can transmit various signals, data, and information on the downlink to the terminal. The processor 1113 may control the operation of the base station apparatus 1110 as a whole.

The base station apparatus 1110 according to an embodiment of the present invention may operate in a wireless communication system supporting downlink MIMO transmission and may support a single user-MIMO or multi-user-MIMO transmission. The processor 1113 of the base station apparatus 1110 transmits downlink control information including information indicating the number of layers to which one or two activated codewords of the downlink MIMO transmission are mapped to the transmission module 1112 Lt; / RTI &gt; The processor 1113 of the base station apparatus 1110 transmits downlink data transmitted on each of the one or more layers and the DMRS for each of the one or more layers based on the downlink control information through the transmission module 1111 . The information indicating the number of layers may further include information on a code identifying the DMRS.

The processor 1113 of the base station apparatus 1110 also performs a function of calculating information received by the base station apparatus 1110 and information to be transmitted to the outside and the memory 1114 stores the processed information and the like at a predetermined time And may be replaced by a component such as a buffer (not shown).

11, the terminal device 1120 according to the present invention may include a receiving module 1121, a transmitting module 1122, a processor 1123, a memory 1124, and a plurality of antennas 1125. The plurality of antennas 1125 means a terminal device supporting MIMO transmission / reception. The receiving module 1121 can receive various signals, data, and information on the downlink from the base station. The receiving module 1122 can transmit various signals, data, and information on the uplink to the base station. The processor 1123 can control the operation of the entire terminal device 1120. [

The terminal device 1120 according to an embodiment of the present invention can operate in a wireless communication system supporting downlink MIMO transmission. The processor 1123 of the terminal device 1120 transmits downlink control information including information indicating the number of layers to which one or two activated codewords of the downlink MIMO transmission are mapped to the reception module 1121 Lt; / RTI &gt; The processor 1123 of the terminal device 1120 is also configured to receive downlink data transmitted on one or more layers based on the downlink control information and a DMRS for each of the one or more layers through the receiving module 1121 . In addition, the processor 1123 of the terminal device 1120 can be configured to demodulate the downlink data based on the DMRS. The information indicating the number of layers may further include information on a code identifying the DMRS.

The processor 1123 of the terminal device 1120 also performs a function of calculating information received by the terminal device 1120 and information to be transmitted to the outside and the memory 1124 stores the processed information and the like at a predetermined time And may be replaced by a component such as a buffer (not shown).

In the case of transmitting UL control information from the terminal apparatus 1120 to the base station apparatus 1110 in a wireless communication system supporting multi-carrier, the following may be commonly applied. The information on the code for identifying the DMRS is information for distinguishing the DMRS transmitted from the same resource element location. When one codeword is mapped to one layer and two codewords are mapped to two layers The information indicating the number of layers can be included in the information. In addition, four DMRSs transmitted from the same resource element are included in one DMRS group, and the one DMRS group is divided into two subgroups according to information on a code for identifying the DMRS, May include two DMRSs separated by an orthogonal code. The downlink control information may further include information indicating an antenna port of the downlink MIMO transmission. The information indicating the number of layers may be composed of 3 bits.

The specific configuration of the base station apparatus and the terminal apparatus may be implemented in the same manner as described in the various embodiments of the present invention described above (that is, various DCI format configurations suggested by the present invention).

The description of the base station apparatus 1110 in the description of FIG. 11 may be similarly applied to a repeater apparatus as a downlink transmission entity or an uplink receiving entity. The description of the terminal apparatus 1120 may be applied to a downlink reception The present invention can be similarly applied to a repeater device as a subject or an uplink transmission entity.

The above-described embodiments of the present invention can be implemented by various means. For example, embodiments of the present invention may be implemented by hardware, firmware, software, or a combination thereof.

In the case of hardware implementation, the method according to embodiments of the present invention may be implemented in one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs) , FPGAs (Field Programmable Gate Arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of an implementation by firmware or software, the method according to embodiments of the present invention may be implemented in the form of a module, a procedure or a function for performing the functions or operations described above. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The foregoing description of the preferred embodiments of the invention disclosed herein has been presented to enable any person skilled in the art to make and use the present invention. While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. For example, those skilled in the art can utilize each of the configurations described in the above-described embodiments in a manner of mutually combining them. Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention. The present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. In addition, claims that do not have an explicit citation in the claims may be combined to form an embodiment or be included in a new claim by amendment after the filing.

1110 base station 1120 terminal
1111, 1121 receiving module 1112, 1122 transmitting module
1113, 1123 Processor 1114, 1124 Memory
1115, 1125 antenna

Claims (12)

A method for transmitting a downlink signal to a mobile station in a wireless communication system supporting downlink multiple input / multiple output (MIMO) transmission through a maximum of eight layers,
Transmitting downlink control information indicating a state of one of a plurality of states indicating a number of layers to which an enabled codeword is mapped for downlink MIMO transmission,
Transmitting downlink data based on the downlink control information,
Wherein each of the plurality of states indicates a number of layers to which the activated codeword is mapped,
The states indicating the number of identical layers according to the number of the activated codewords among the plurality of states include information for identifying a UE-specific reference signal for demodulating the downlink data different from each other The method comprising the steps of: The method according to claim 1,
Wherein the number of active codewords is one or two. 3. The method of claim 2,
Wherein the one state indicates the number of different layers according to the number of activated codewords. The method according to claim 1,
In the case where the activated codeword is 1, states indicating 1 as the number of layers among the plurality of states further include information for identifying a UE-specific reference signal for demodulating the downlink data Directed,
In the case where the number of active codewords is two, states indicating 2 as the number of layers among the plurality of states further include information for identifying a UE-specific reference signal for demodulating the downlink data The method comprising the steps of: The method according to claim 1,
Wherein the plurality of states are a maximum of eight states. A method for receiving a downlink signal from a base station in a wireless communication system supporting downlink multiple input / multiple output (MIMO) transmission through a maximum of eight layers,
Receiving downlink control information indicating a state of one of a plurality of states indicating a number of layers to which an enabled codeword is mapped for downlink MIMO transmission,
Receiving downlink data based on the downlink control information,
Wherein each of the plurality of states indicates a number of layers to which the activated codeword is mapped,
The states indicating the number of identical layers according to the number of the activated codewords among the plurality of states include information for identifying a UE-specific reference signal for demodulating the downlink data different from each other The method comprising the steps of: The method according to claim 6,
Wherein the number of activated codewords is one or two. 8. The method of claim 7,
Wherein the one state indicates the number of different layers according to the number of activated codewords. The method according to claim 6,
In the case where the activated codeword is 1, states indicating 1 as the number of layers among the plurality of states further include information for identifying a UE-specific reference signal for demodulating the downlink data Directed,
In the case where the number of active codewords is two, states indicating 2 as the number of layers among the plurality of states further include information for identifying a UE-specific reference signal for demodulating the downlink data And transmitting the downlink signal. The method according to claim 6,
Wherein the plurality of states are a maximum of eight states. A base station for transmitting a downlink signal to a mobile station in a wireless communication system supporting downlink multiple input / multiple output (MIMO) transmission through a maximum of eight layers,
A receiving module for receiving uplink control information and uplink data from the terminal;
A transmission module for transmitting downlink control information and downlink data to the terminal; And
And a processor for controlling the base station including the receiving module and the transmitting module,
The processor comprising:
Controls the transmitting module to transmit downlink control information indicating a state of a plurality of states indicating a number of layers to which a codeword is enabled for downlink MIMO transmission, ,
Controlling the transmission module to transmit downlink data based on the downlink control information,
Wherein each of the plurality of states indicates a number of layers to which the activated codeword is mapped,
The states indicating the number of identical layers according to the number of the activated codewords among the plurality of states include information for identifying a UE-specific reference signal for demodulating the downlink data different from each other Downlink signaling base station. A terminal for receiving a downlink signal from a base station in a wireless communication system supporting downlink multiple input / output (MIMO) transmission through a maximum of eight layers,
A receiving module for receiving downlink control information and downlink data from the base station;
A transmission module for transmitting uplink control information and uplink data to the base station; And
And a processor for controlling the terminal including the receiving module and the transmitting module,
The processor comprising:
Controls the receiving module to receive downlink control information indicating one of a plurality of states indicating a number of layers to which a codeword is enabled to be mapped for downlink MIMO transmission, ,
Controlling the receiving module to receive downlink data based on the downlink control information,
Wherein each of the plurality of states indicates a number of layers to which the activated codeword is mapped,
The states indicating the number of identical layers according to the number of the activated codewords among the plurality of states include information for identifying a UE-specific reference signal for demodulating the downlink data different from each other Downlink signal receiving terminal.

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